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Asbestos is a naturally occurring group of fibrous silicate minerals. There are six recognized asbestos mineral types: chrysotile, amosite, crocidolite, tremolite asbestos, actinolite asbestos, and anthophyllite asbestos. These minerals can separate into extremely small, durable fibers that may become airborne when asbestos-containing materials are cut, drilled, sanded, scraped, broken, demolished, or otherwise disturbed. CalDIR

Because asbestos fibers are strong, heat resistant, chemically resistant, and durable, asbestos was historically incorporated into thousands of commercial and construction products. It was commonly used for fire resistance, thermal insulation, acoustical properties, reinforcement, and durability.

Although many asbestos-containing products are no longer manufactured or commonly used in the United States, legacy asbestos-containing materials remain present in countless homes, commercial buildings, schools, industrial facilities, and other structures.

California has an especially interesting relationship with asbestos. Serpentinite, commonly referred to as serpentine, is California's official State Rock, while gold is the State Mineral. Serpentinite occurs naturally throughout portions of California and may contain chrysotile asbestos, the most common form of asbestos. California Department of Conservation

This means asbestos concerns in California are not limited to manufactured building materials. 

Naturally occurring asbestos (NOA) can also be encountered in certain rock and soil formations and may become airborne when asbestos-bearing rock is disturbed by grading, excavation, construction, quarrying, or vehicle traffic on unpaved surfaces. California Air Resources Board

Asbestos can be present in many different building materials, and its appearance can vary considerably. Common suspect materials include, but are not limited to:

• Acoustic or “popcorn” ceiling texture
• Drywall joint compound, skim coats, and wall or ceiling texture
• Plaster and patching compounds
• Resilient floor tile
• Sheet vinyl or linoleum flooring and backing
• Flooring mastics, adhesives, and glues
• Thermal-system and pipe insulation
• Boiler and furnace insulation
• HVAC duct insulation, seam tape, and vibration materials
• Fireproofing and sprayed-on insulation
• Some attic insulation, particularly vermiculite
• Roofing felts, mastics, coatings, and shingles
• Exterior stucco and cementitious coatings
• Transite asbestos-cement siding, panels, and flue pipes
• Window glazing and some caulking compounds
• Electrical and heat-resistant components
• Gaskets and packing materials
• Other specialty construction products

The presence of asbestos cannot reliably be determined simply by looking at a material. A material may look identical to a non-asbestos product sitting next to it.

The most reliable method is to obtain a representative bulk sample and have it analyzed by a qualified laboratory.

Polarized Light Microscopy (PLM) is the primary analytical method used to identify asbestos in bulk building materials. The laboratory microscopically examines the material to determine whether asbestos fibers are present and, when detected, estimates or measures the asbestos content. EPA NEEPA

Depending on the material and laboratory result, additional analysis may sometimes be appropriate. For example, point-count analysis may be requested to more precisely quantify low-level asbestos findings, while Transmission Electron Microscopy (TEM) may be appropriate for certain specialized applications.

Sampling is also important. Different materials, layers, applications, and visually distinct areas may represent separate homogeneous materials and may require separate samples. A laboratory result is only as representative as the sampling that produced it.

Asbestos-containing material that is intact, in good condition, and left undisturbed is generally much less likely to create an exposure hazard. EPA guidance states that asbestos material in good condition and left undisturbed is unlikely to present a health risk. US EPA

The primary concern occurs when asbestos-containing material becomes damaged, deteriorated, friable, or disturbed. Activities such as demolition, sanding, grinding, drilling, sawing, scraping, removing flooring, opening walls and ceilings, or improperly removing asbestos-containing material can release microscopic fibers into the air.

These fibers may remain suspended for extended periods depending on fiber size, air movement, ventilation, HVAC operation, and other environmental conditions. Airborne fibers can also migrate beyond the immediate work area and settle onto surfaces, furnishings, clothing, and personal belongings.

This is why an asbestos problem that begins as a relatively small amount of material can become a much larger airborne exposure and cross-contamination issue when demolition or renovation is performed improperly.

Asbestos fibers are microscopic and can be inhaled deep into the lungs. Exposure to airborne asbestos has been associated with serious diseases including asbestosis, lung cancer, mesothelioma, and pleural disease. Evidence also links asbestos exposure to certain other cancers. Many asbestos-related diseases have long latency periods and may not become apparent until decades after exposure. ATSDR

There is no established safe threshold for inhalation exposure to asbestos. At the same time, asbestos risk is related to factors such as the amount of airborne asbestos, duration and frequency of exposure, cumulative exposure, fiber characteristics, and individual risk factors. Most documented asbestos disease historically occurred among individuals who experienced substantial occupational exposure over prolonged periods. US EPA

Workers in demolition, remodeling, construction, insulation, maintenance, and other trades can face increased exposure when asbestos-containing materials are repeatedly disturbed without appropriate controls.

Cigarette smoking combined with asbestos exposure also greatly increases the risk of lung cancer compared with either risk factor alone. ATSDR

California property owners and contractors frequently hear the terms ACM and ACCM, but they do not mean exactly the same thing.

Asbestos-Containing Material (ACM) generally refers to material containing more than 1% asbestos. CalDIR

California Cal/OSHA also recognizes Asbestos-Containing Construction Material (ACCM), defined as manufactured construction material containing more than 0.1% asbestos by weight. CalDIR

This distinction is important because a construction material reported below 1% asbestos is not automatically irrelevant or unregulated in California. Worker-protection, training, work-practice, registration, notification, and other requirements may depend on the asbestos concentration, quantity of material being disturbed, type of work, and applicable regulation.

One of the most common ways accidental asbestos exposure occurs is when remodeling or demolition begins before suspect materials are evaluated.

Older homes and buildings have a greater likelihood of containing legacy asbestos materials, but building age and appearance alone cannot confirm or rule out asbestos. If suspect building materials are going to be cut, removed, scraped, demolished, sanded, drilled, or otherwise disturbed, they should be evaluated before work begins.

Depending on the type of structure, materials involved, quantity being disturbed, and jurisdiction, asbestos survey, sampling, notification, work-practice, and abatement requirements may apply. In the Bay Area, asbestos-related demolition and renovation activities may fall under Bay Area Air Quality Management District Regulation 11, Rule 2, in addition to applicable Cal/OSHA and federal requirements. BAAQMD's rule also contains specific provisions and exceptions for certain residential buildings, so requirements should be evaluated based on the actual project. BAAQMD

Failing to identify asbestos before construction can result in unnecessary worker and occupant exposure, contamination of otherwise unaffected areas, work stoppages, additional cleanup expenses, disposal issues, regulatory problems, project delays, and potential liability.

Asbestos work should not be treated like ordinary demolition.

California has specific licensing, certification, registration, training, notification, respiratory-protection, containment, work-practice, and waste-handling requirements for asbestos-related work. The requirements depend on factors including the type and quantity of material and the work being performed.

For asbestos-related work involving 100 square feet or more of asbestos-containing material, California generally requires an appropriately licensed/certified asbestos contractor, and applicable Cal/OSHA/DOSH registration requirements also apply. Work involving smaller quantities is not simply unregulated; worker-training, notification, exposure-control, and other Cal/OSHA requirements can still apply. CalDIR

A typical general contractor, remodeling contractor, maintenance worker, or handyman should therefore never assume that asbestos can be removed like ordinary construction debris simply because the amount appears small.

Testing before construction is substantially easier than investigating a property after an unknown material has already been demolished and spread throughout the building.

When asbestos is identified in advance, the owner and contractor can plan the project appropriately, determine applicable regulatory requirements, protect workers and occupants, and prevent avoidable contamination.

When in doubt — test before you disturb.

Lead is a naturally occurring metal that was historically added to paint and coatings to improve durability, accelerate drying, provide color, and increase resistance to moisture and corrosion.

Lead compounds were used extensively in residential, commercial, and industrial coatings for many decades. In 1978, the federal government severely restricted the use of lead in residential consumer paint. As a result, homes and residential buildings constructed before 1978 are more likely to contain lead-based paint, and the older the structure, the greater the likelihood that lead-containing coatings may be present. US EPA

The 1978 date should not automatically be applied to every type of structure or coating. Lead-containing coatings may still be encountered on steel structures, industrial equipment, tanks, bridges, machinery, and other specialty applications, including coatings applied after 1978. California Department of Public Health

Lead-based paint may be present on interior and exterior painted surfaces, including:

• Walls and ceilings
• Doors and door frames
• Windows, window sashes, and window trim
• Baseboards and other woodwork
• Cabinets and built-in components
• Railings, stairs, and porches
• Exterior siding and trim
• Painted metal surfaces
• Structural steel and industrial coatings
• Older painted furniture and other painted components

Multiple generations of paint are common in older structures. A newer lead-free topcoat does not necessarily mean that older underlying paint layers are lead-free.

The presence of lead-based paint does not automatically mean that occupants are being exposed.

Lead becomes a greater concern when painted surfaces are deteriorated, peeling, chipping, chalking, damaged, or disturbed. Friction and impact surfaces such as windows and doors can also generate lead-containing dust over time.

Renovation, repair, demolition, sanding, scraping, grinding, cutting, drilling, or improper paint removal can convert previously intact lead-containing coatings into fine dust and debris that can spread beyond the immediate work area.

Lead dust can settle onto floors, countertops, window sills, furnishings, carpeting, toys, clothing, and other surfaces. Exterior paint deterioration or improper exterior preparation can also contribute lead contamination to surrounding soil.

This distinction is important.

Lead-based paint refers to the concentration of lead contained within paint or another surface coating.

A lead hazard generally involves a condition capable of causing harmful exposure, such as deteriorated lead-based paint, lead-contaminated dust, lead-contaminated soil, or work that disturbs lead-based paint without appropriate controls.

In California, a deteriorated painted surface, contaminated dust or soil, or disturbance of lead-based or presumed lead-based paint without proper containment may constitute a lead hazard. California Department of Public Health

You generally cannot determine whether paint contains lead simply by looking at it.

Professional evaluation may include an X-ray fluorescence (XRF) instrument or representative paint-chip samples submitted to a qualified laboratory for analysis.

Consumer lead test kits are available, but they have limitations. EPA recommends professional evaluation when determining whether a home contains lead-based paint. EPA-recognized test kits used for RRP compliance are intended for use by trained professionals, and EPA notes that no currently recognized test kit has satisfied both its positive- and negative-response performance criteria. US EPA

For a pre-1978 structure undergoing renovation, another option is to presume that affected painted surfaces contain lead-based paint and use the required lead-safe work practices rather than attempting to rule it out. US EPA

Under federal and California standards, lead-based paint generally means paint or another surface coating containing lead at or above:

1.0 milligram per square centimeter (mg/cm²)

or 0.5% lead by weight — equivalent to 5,000 parts per million (ppm). California Department of Public Health

It is important to understand that paint containing lead below the regulatory definition of “lead-based paint” is not necessarily harmless. Construction activities can still create occupational lead exposure, and worker-protection requirements may apply when lead-containing materials are disturbed. OSHA

Lead can enter the body primarily by inhalation or ingestion. Young children are particularly vulnerable because of normal hand-to-mouth behavior and because their developing nervous systems are especially sensitive to lead.

Lead exposure can affect the brain and nervous system and may also affect the kidneys, blood-forming system, cardiovascular system, and other organs. Children may experience learning, behavioral, developmental, and neurological effects.

Adults can also be exposed, particularly through occupational activities such as construction, painting, demolition, abrasive blasting, sanding, welding or torch cutting of lead-coated materials, and other work involving lead-containing products.

A person with elevated lead exposure may have no obvious symptoms, particularly at lower levels. A blood lead test is the primary method used to determine how much lead is present in the body. California health guidance states that harmful effects may occur at very low blood lead levels. California Department of Public Health

There is no identified blood lead level known to be completely free of risk for children.

The CDC currently uses a Blood Lead Reference Value (BLRV) of 3.5 micrograms per deciliter (µg/dL) for children. The BLRV is used to identify children whose blood lead levels are higher than most children in the United States; it is not a dividing line between “safe” and “unsafe.” CDC

For adults, the California Department of Public Health recommends clinical follow-up for blood lead levels of 3.5 µg/dL or greater. The mean blood lead level for U.S. adults is less than 1 µg/dL. California Department of Public Health

One of the most significant hazards associated with renovation is not necessarily the visible paint chip — it is the fine lead-containing dust created when painted surfaces are disturbed.

Sanding, scraping, grinding, demolition, window replacement, saw cutting, drilling, and uncontrolled cleanup can distribute dust throughout a home or building.

California currently defines lead-contaminated dust under Title 17 at concentrations of:

Interior floors: 10 µg/ft² or greater
Interior horizontal surfaces: 100 µg/ft² or greater
Exterior floors and horizontal surfaces: 400 µg/ft² or greater. California Department of Public Health

Federal EPA standards were strengthened again in 2024. EPA now treats any reportable laboratory level of lead in dust as its federal dust-lead reportable level and established post-abatement dust-lead action levels of 5 µg/ft² for floors, 40 µg/ft² for window sills, and 100 µg/ft² for window troughs under EPA-administered programs. Because California operates its own authorized lead program, the regulatory criteria applicable to a particular project should be determined based upon the jurisdiction and type of work being performed. US EPA

Renovation is one of the most common ways occupants and workers are unintentionally exposed to lead.

EPA's Renovation, Repair and Painting (RRP) Rule generally applies to contractors and other firms receiving compensation for work that disturbs painted surfaces in pre-1978 housing and child-occupied facilities.

Covered firms must be EPA Lead-Safe Certified, use appropriately trained personnel, contain the work area, minimize dust generation, properly clean the work area, and maintain required records. US EPA

Subject to applicable exceptions, the rule generally covers work disturbing more than 6 square feet of painted surface per room on the interior or 20 square feet on the exterior. Window replacement is also a covered activity. US EPA

Homeowners performing work themselves in their own owner-occupied residence are generally not subject to the federal RRP certification requirement, but EPA strongly recommends following the same lead-safe practices because DIY renovation can still create significant lead dust. US EPA

This is another important distinction.

Renovation, Repair and Painting (RRP) refers to ordinary construction work that happens to disturb lead-based or presumed lead-based paint.

Lead abatement is work specifically designed to permanently reduce or eliminate lead-based paint or lead hazards.

In California, individuals who are paid to conduct formal lead inspections, risk assessments, or lead clearance inspections in residential or public buildings must have the appropriate California Department of Public Health Lead-Related Construction certification. Individuals performing regulated lead-abatement work are also subject to California certification and work-practice requirements. California Department of Public Health

Discovering lead before renovation is much easier than discovering it after painted materials have already been sanded, demolished, or distributed throughout a property.

Pre-construction testing can help property owners and contractors:

• Identify affected painted components
• Determine which regulatory requirements apply
• Plan appropriate containment and work practices
• Protect workers and occupants
• Prevent cross-contamination
• Avoid unnecessary cleanup and project delays
• Document conditions before construction begins

Improperly disturbing lead-containing paint can transform a manageable building material issue into a much larger dust-contamination and exposure problem.

When working on an older home, commercial property, or painted structure, never assume that paint is lead-free based only on appearance or condition.

Identify the material first. Plan the work correctly. Prevent the contamination before it occurs.

Mold is a type of fungus that grows naturally throughout the environment. Thousands of different species exist, and mold can appear in many colors, including black, green, white, gray, brown, yellow, and orange.

Mold reproduces by releasing microscopic spores into the air. These spores are a normal part of both indoor and outdoor environments. The presence of mold spores alone does not necessarily indicate an indoor mold problem. A problem develops when excessive moisture allows mold to actively grow on building materials, furnishings, or other indoor surfaces.

Mold can grow on or within many common materials, including drywall, wood, paper, insulation, carpet, ceiling tiles, fabrics, dust, and other organic matter. The key ingredient that allows indoor mold growth to develop is moisture. EPA describes moisture control as the fundamental method of controlling indoor mold. US EPA

Indoor mold growth is almost always associated with an underlying moisture condition.

Common sources include:

• Plumbing leaks
• Roof leaks
• Window or exterior-envelope leaks
• Shower and bathtub leakage
• Toilet or appliance leaks
• Water intrusion from storms or flooding
• Crawlspace moisture
• Poor drainage around the foundation
• Condensation
• Elevated indoor humidity
• HVAC or condensate problems
• Wet building materials following construction
• Improperly dried areas after previous water damage

Moisture is not always obvious. Water can migrate behind drywall, beneath flooring, inside cabinets, under shower assemblies, within ceilings, or into wall and floor cavities where the surface may appear dry.

This is why professional mold inspections often involve more than simply looking for visible growth. Moisture meters, thermal imaging, visual inspection, building-history information, and selective sampling can help identify conditions that may otherwise remain concealed.

Water-damaged materials should be dried as quickly as possible.

EPA recommends drying wet or damp materials within approximately 24 to 48 hours whenever possible because prolonged moisture greatly increases the likelihood of mold growth. This does not mean every wet material will automatically grow mold at exactly 48 hours; temperature, material type, humidity, airflow, and the extent of wetting all influence growth. US EPA

The important point is simple:

The longer building materials remain wet, the greater the potential for mold growth and concealed moisture damage.

Allowing a water-damaged wall, floor, or ceiling to simply “air dry” may not adequately dry concealed materials inside the building cavity.

Yes. Some of the most significant mold conditions are not immediately visible.

Hidden mold may develop:

• Behind drywall
• Under flooring
• Beneath cabinets
• Behind baseboards
• Inside wall or ceiling cavities
• Beneath shower pans
• Around plumbing penetrations
• Beneath roofing or sheathing
• Within crawlspaces or attics
• Around HVAC equipment or duct systems

A musty or earthy odor may suggest microbial growth or damp building materials, but an odor alone does not prove the presence, species, or extent of mold.

Likewise, the absence of an odor does not guarantee that hidden mold is absent.

People respond differently to mold exposure.

According to CDC, damp and moldy environments may cause no noticeable effects in some individuals, while others may experience nasal congestion, coughing, wheezing, eye irritation, skin irritation, or allergic reactions. Mold exposure has also been associated with worsening asthma in susceptible individuals. CDC

Individuals with asthma, mold allergies, chronic lung disease, or weakened immune systems may be more susceptible to adverse effects. CDC advises that people with certain respiratory conditions or significant immune suppression avoid entering heavily mold-damaged environments. CDC

It is important not to assume that every symptom experienced inside a building is caused by mold. Indoor air quality complaints may involve many possible factors, and medical concerns should be evaluated by an appropriate healthcare professional.

The term “black mold” is commonly used by the public, but it is not a scientific diagnosis of a building condition.

Many different mold species can appear dark green, brown, gray, or black. The color of mold alone does not determine whether it is dangerous.

One species frequently associated with the term is Stachybotrys chartarum, but identifying mold by appearance alone is unreliable. More importantly, any significant indoor mold growth indicates an underlying moisture problem that should be corrected, regardless of color or species.

There is currently no federal EPA exposure standard or regulatory threshold for airborne mold spores in indoor environments. EPA specifically states that there are no federal standards or Threshold Limit Values for airborne mold concentrations. California likewise does not have a science-based numerical indoor mold exposure limit. US EPA

For this reason, mold air sampling should not be interpreted as a simple “safe” or “unsafe” numerical test.

Professional interpretation may consider factors such as:

• Indoor versus outdoor spore concentrations
• Types of spores detected
• Relative distribution between areas
• Presence of unusual or moisture-associated fungal types indoors
• Visual evidence
• Moisture conditions
• Building history
• Occupant complaints
• Whether remediation has recently occurred

Air sampling represents conditions at the time and location sampled and should be interpreted together with the physical inspection.

Not necessarily.

If obvious mold growth and an obvious moisture source are present, EPA states that sampling may not be necessary before cleanup. US EPA

Testing can still be useful in situations such as:

• Suspected hidden mold
• Unexplained musty odors
• Water-damage history without visible growth
• Real-estate due diligence
• Occupant complaints
• Establishing baseline indoor conditions
• Evaluating areas adjacent to known contamination
• Post-remediation clearance
• Documenting conditions before or after construction

The purpose of testing should be defined before samples are collected.

Successful mold remediation requires more than applying a chemical to a stained surface.

The primary objectives are to:

1. Identify and correct the moisture source
2. Remove unsalvageable mold-contaminated porous materials
3. Clean salvageable surfaces
4. Prevent contamination from spreading to unaffected areas
5. Dry remaining materials and structural components
6. Verify that the work area is clean and dry before reconstruction

EPA emphasizes that mold should be physically removed, not merely killed. Dead mold can still contain allergenic material, and routine use of biocides or disinfectants is not considered a substitute for proper removal and cleaning. US EPA

Removing mold-damaged drywall, insulation, flooring, or other materials can release large quantities of spores and particulate debris.

For larger or more invasive projects, appropriate controls may include:

• Polyethylene containment barriers
• Sealing doors, openings, and penetrations
• Protecting or isolating HVAC registers
• HEPA-filtered air filtration or negative-air equipment
• HEPA vacuuming
• Controlled removal of damaged materials
• Proper disposal procedures
• Personal protective equipment
• Respiratory protection when appropriate

The level of containment should be based on the size, location, severity, and nature of the remediation project.

EPA notes that disturbance of mold-contaminated porous materials and invasive work inside wall cavities can significantly increase airborne exposure, which is why proper PPE and work-area controls are important. US EPA

There is no universal rule requiring removal exactly 12 inches, 24 inches, or any other fixed distance beyond visible mold.

The appropriate removal boundary should be based on actual field conditions.

Remediation should continue until mold growth, moisture damage, deteriorated materials, and affected substrates have been adequately addressed and clean, dry, sound materials remain.

In some situations the affected area may extend only slightly beyond what is visible. In others, concealed moisture may have traveled considerably farther.

This is why opening a wall or ceiling can sometimes reveal substantially more damage than was visible from the occupied space.

Removing damaged drywall or other mold-contaminated material is only part of the remediation process.

Remaining framing, subflooring, sheathing, concrete, and other structural materials must be adequately dried before new materials are installed.

Reconstructing over damp substrates can trap moisture inside the assembly and create conditions for the mold problem to return.

Depending on site conditions, drying may involve:

• Dehumidification
• Controlled air movement
• Moisture monitoring
• HVAC adjustments
• Removal of wet insulation or other materials
• Additional access to concealed cavities

The moisture source must also be repaired. If the underlying moisture problem remains, mold remediation alone will not solve the problem.

Chemical treatment should not replace physical cleaning and removal.

EPA does not recommend routine use of biocides such as chlorine bleach as the primary method of mold remediation. California public-health guidance likewise cautions that disinfectants and fungicides are often unnecessary and that antimicrobial fogging or misting alone is not an effective substitute for removal. US EPA

Specialized antimicrobial products or protective coatings may sometimes be used when appropriate for the material and project, but they should be considered supplemental measures, not a way to cover over unresolved mold or moisture damage.

Small, isolated areas may sometimes be handled safely by a knowledgeable property owner depending on the circumstances.

Larger areas, concealed contamination, sewage-related water damage, extensive building-material removal, HVAC involvement, or situations involving susceptible occupants are better suited for experienced restoration or mold-remediation professionals.

California currently has no state license specifically called a “mold-remediation license” or “mold-inspector license.” However, companies performing construction or building-improvement work may still be required to hold an appropriate California contractor license depending on the scope and value of the work. Property owners should also look for specific mold-remediation training, experience, appropriate insurance, and recognized industry certifications. California Department of Public Health

An important final step following professional mold remediation is determining whether the work was successfully completed before containment is removed and reconstruction begins.

A post-remediation assessment may include:

• Visual inspection of the containment and work area
• Verification that visible mold and debris have been removed
• Confirmation that remaining materials are adequately dry
• Inspection of cleaned structural substrates
• Evaluation of dust and cleanliness
• Air sampling when appropriate

EPA recognizes that post-remediation sampling may be useful for evaluating whether cleanup efforts were effective. When air sampling is performed, results are typically interpreted in relation to outdoor conditions and the overall inspection rather than against a federal numerical “pass/fail” mold standard. US EPA

Mold is ultimately a moisture problem.

Finding mold without determining why it grew addresses only half of the issue.

Identify the moisture source. Correct it. Remove the affected materials. Dry the structure. Verify the cleanup before reconstruction.

Indoor Air Quality (IAQ) refers to the condition of the air inside homes, offices, schools, and other buildings as it relates to the health, comfort, and well-being of the people occupying them.

Indoor air can be affected by pollutants generated inside the building, contaminants entering from outdoors, moisture and biological growth, building materials and furnishings, occupant activities, combustion appliances, and the performance of the heating, ventilation, and air-conditioning system.

The U.S. Environmental Protection Agency estimates that people spend approximately 90% of their time indoors, and concentrations of some pollutants can be several times higher indoors than outdoors. US EPA

A home does not need to look dirty or have an obvious odor to have an indoor air quality concern. Many indoor contaminants are invisible and odorless.

Indoor air quality can be affected by many different sources and conditions, including:

• Mold and excessive moisture
• Volatile Organic Compounds (VOCs)
• Formaldehyde
• Fine particulate matter (PM2.5)
• Carbon monoxide (CO)
• Carbon dioxide (CO₂) and inadequate ventilation
• Combustion byproducts
• Nitrogen dioxide (NO₂)
• Radon
• Smoke and wildfire particulates
• Tobacco and vaping aerosols
• Pollen
• Dust and dust mites
• Pet dander
• Bacteria and other biological contaminants
• Pesticides and household chemicals
• Cleaning and disinfecting products
• New furniture, flooring, cabinetry, paint, and building materials
• Construction and renovation dust
• Asbestos fibers when asbestos-containing materials are disturbed
• Lead-containing dust
• Vehicle exhaust and attached garages
• HVAC systems, filters, ducts, and condensate components
• Outdoor contaminants entering through windows, doors, cracks, or ventilation systems

EPA identifies carbon monoxide, particulate matter, mold, radon, VOCs, biological contaminants, nitrogen dioxide and smoke among important indoor pollutants and sources. US EPA

One common misconception is that an indoor air quality investigation is simply a mold test.

Mold is only one possible component of IAQ.

A building may have acceptable mold conditions but still have elevated particulate matter, chemical emissions, inadequate ventilation, combustion pollutants, formaldehyde, or another source affecting the indoor environment.

Likewise, an unusual odor does not automatically mean mold. Odors may originate from:

• Building materials
• Flooring or adhesives
• Cabinetry
• Cleaning products
• Sewer or plumbing conditions
• Combustion appliances
• Stored chemicals
• HVAC components
• Moisture-damaged materials
• Off-gassing furnishings
• Adjacent garages or exterior sources

This is why an IAQ investigation should begin by asking what is happening inside the building and what potential sources need to be evaluated, rather than randomly testing for everything.

Biological contaminants can include mold, bacteria, viruses, pollen, dust mites, pet allergens, insects, rodents and their associated debris or allergens. EPA recognizes these as potential contributors to indoor air quality problems. US EPA

Some amount of biological material is present in virtually every occupied building. The goal is not to create a completely sterile indoor environment.

Concerns arise when building conditions allow unusual accumulation or amplification—for example, when excessive moisture supports mold growth or poorly maintained equipment accumulates biological debris.

Moisture, nutrients, temperature, and airflow all influence biological growth. Bathrooms, kitchens, crawlspaces, attics, HVAC components, carpeting, wall cavities, and previously water-damaged areas can become problem locations under the right conditions. Your original material correctly emphasizes moisture as one of the most important underlying factors. 

Excessive moisture is one of the most common contributors to indoor environmental problems.

Potential sources include:

• Plumbing leaks
• Roof leaks
• Shower or tub leakage
• Window or exterior wall intrusion
• Crawlspace moisture
• Poor site drainage
• Condensation
• Wet foundations
• Appliance leaks
• HVAC condensate problems
• Elevated indoor humidity
• Past flooding or water damage

Moisture can also be hidden inside walls, ceilings, floors, cabinets, crawlspaces, and other inaccessible locations.

A surface may feel dry even though underlying materials remain wet.

Warning signs can include water staining, peeling paint, damaged flooring, condensation, musty odors, swollen materials, deterioration, or a history of water intrusion. Your existing education material already identifies many of these clues and locations appropriately. 

Ventilation is an important component of indoor air quality.

Buildings require adequate outdoor-air exchange to help dilute contaminants generated indoors and remove excess moisture, odors, and other pollutants.

A tightly constructed or poorly ventilated building can allow contaminants to accumulate even when there is no single dramatic pollution source.

Carbon dioxide (CO₂) can sometimes be measured as an indicator of ventilation and occupant-generated air accumulation. 

CO₂ measurements must be interpreted carefully because occupancy, room size, outdoor concentrations, ventilation rates, and when and where the measurement was obtained all affect the result. EPA specifically cautions that indoor CO₂ can provide useful ventilation information but should not be interpreted in isolation. US EPA

CO₂ should also not be confused with carbon monoxide (CO). They are very different gases.

Carbon monoxide is a colorless and odorless gas produced by incomplete combustion. Potential sources include furnaces, water heaters, fireplaces, gas appliances, generators, vehicles, and improperly vented or malfunctioning combustion equipment.

Other combustion pollutants may include nitrogen dioxide and fine particulate matter.

Improper installation, inadequate ventilation, defective equipment, backdrafting, blocked flues, or operation of combustion equipment in inappropriate locations can allow pollutants to enter occupied areas. US EPA

Every home with combustion equipment or an attached garage should have properly located and functioning carbon monoxide alarms. Professional IAQ testing is not a substitute for required life-safety alarms.

PM2.5 refers to fine particles approximately 2.5 micrometers in diameter or smaller.

Because of their extremely small size, these particles can penetrate deeply into the respiratory system.

Indoor PM2.5 can originate from outdoor pollution as well as indoor activities such as:

• Cooking
• Frying or grilling
• Burning candles
• Fireplaces and wood stoves
• Tobacco smoke
• Some cleaning activities
• Construction dust
• Combustion appliances
• Biological material

Outdoor particles can also infiltrate indoors through doors, windows, wall penetrations, ventilation systems, and normal building leakage. US EPA

For California residents, indoor air quality can also be strongly affected by wildfire smoke and regional outdoor air pollution.

Closing windows and doors may reduce smoke infiltration, but outdoor PM2.5 can still enter a structure through normal leakage and ventilation pathways. Filtration, properly operated HVAC systems, and portable air cleaners can help reduce indoor particle concentrations during smoke events. US EPA

This is an important reminder that an indoor air quality problem does not always originate indoors.

Volatile Organic Compounds (VOCs) are chemicals that can evaporate into the air from many common products and building materials.

Potential sources include:

• Paints and coatings
• Adhesives
• Flooring
• Carpeting
• Cabinets
• Furniture
• Solvents
• Cleaning products
• Air fresheners
• Personal-care products
• Stored fuels and chemicals
• Remodeling materials

EPA reports that concentrations of many VOCs can be higher indoors than outdoors. US EPA

New construction and recently remodeled buildings can sometimes experience elevated chemical emissions because multiple new materials may be off-gassing simultaneously.

Formaldehyde is a specific VOC that may be emitted from building materials, furnishings, adhesives, household products, and combustion sources.

Pressed-wood products such as particleboard, medium-density fiberboard (MDF), cabinetry, furniture, and some composite wood products can be important indoor sources. US EPA

Formaldehyde concerns may be particularly relevant following:

• Installation of new cabinetry
• New flooring
• New furniture
• Major remodeling
• New construction
• Installation of composite wood products

Testing formaldehyde separately from a general VOC screening can provide more specific information when formaldehyde is a suspected concern.

Radon is a naturally occurring radioactive gas that enters buildings from the soil and geology beneath them.

It cannot be seen, smelled, or tasted.

The only way to know the radon concentration in a building is to test for it. EPA recommends that all homes be tested for radon. US EPA

Radon conditions can vary considerably from one property to another, meaning that a neighbor's result does not establish the radon level in your home.

Heating and air-conditioning systems can have a major influence on IAQ because they circulate air throughout the building.

Potential concerns may include:

• Dirty or improperly installed filters
• Damaged ductwork
• Dust accumulation
• Condensate problems
• Dirty coils
• Poorly maintained drain pans
• Inadequate outdoor-air ventilation
• Improper air balance
• Moisture within equipment
• Contaminated duct insulation
• Air leakage from attics, crawlspaces, garages, or other spaces

HVAC maintenance and filter replacement should be performed in accordance with the equipment and filter manufacturer's specifications rather than using a single replacement interval for every system.

Your original material appropriately emphasizes inspecting and maintaining HVAC equipment, humidifiers, dehumidifiers and other appliances that interact with moisture and indoor air. 

Indoor environmental conditions may contribute to symptoms such as:

• Eye, nose, or throat irritation
• Sneezing
• Nasal congestion
• Coughing
• Wheezing
• Headaches
• Fatigue
• Dizziness
• Respiratory irritation
• Aggravation of allergies or asthma

However, these symptoms are nonspecific and may have many causes unrelated to the building.

A useful clue is sometimes the pattern of the complaint. For example, symptoms that consistently appear in a particular building and improve after leaving may justify further investigation. Your existing material correctly raises this type of building-related comparison. 

Environmental testing does not diagnose medical conditions. Anyone experiencing persistent or significant symptoms should discuss them with an appropriate healthcare professional.

This is extremely important.

There is no single laboratory sample, instrument, or air test that can determine whether everything about the air inside a building is safe.

An effective IAQ investigation should first identify the concern and potential sources. Testing can then be selected based on what is actually suspected.

Depending on the property and concern, an evaluation may include:

• Visual building inspection
• Moisture measurements
• Thermal imaging
• Mold air sampling
• Particulate measurements
• PM2.5 monitoring
• VOC screening or laboratory analysis
• Formaldehyde testing
• Carbon dioxide measurements
• Carbon monoxide measurements
• Radon testing
• Assessment of HVAC and ventilation conditions
• Targeted testing for specific contaminants

Randomly collecting multiple samples without understanding the building can create numbers without necessarily identifying the problem.

Consumer air-quality monitors can be useful for identifying trends, but they do not necessarily provide a complete environmental assessment.

A sensor may detect an increase in particles, VOCs, or CO₂ without determining what caused the increase.

EPA cautions that low-cost monitor readings alone generally cannot determine an individual's health risk because exposure, personal susceptibility, instrument performance, and other environmental factors must also be considered. US EPA

Professional interpretation should therefore consider the instrument readings together with the building conditions and potential sources.

EPA identifies three fundamental approaches to improving indoor air:

1. Source Control
Remove, repair, isolate, or reduce the source of contamination whenever possible.

2. Ventilation
Introduce appropriate outdoor air and exhaust pollutants and excessive moisture to the exterior.

3. Filtration and Air Cleaning
Use properly selected filtration or supplemental air-cleaning equipment to help reduce airborne contaminants. US EPA

Other important steps may include correcting water intrusion, maintaining HVAC equipment, controlling humidity, using kitchen and bathroom exhaust ventilation, properly venting dryers and combustion equipment, reducing unnecessary chemical products, and keeping occupied areas clean.

An IAQ investigation may be appropriate when:

• Occupants notice persistent unusual or chemical odors
• A building has experienced water damage
• Occupants experience recurring symptoms associated with a particular location
• Mold is suspected but not readily visible
• A home has recently been remodeled
• New flooring, cabinetry, furniture, or coatings have been installed
• The indoor environment feels unusually stale or poorly ventilated
• Excessive dust or particulate matter is present
• Wildfire smoke or outdoor pollution may be entering the structure
• HVAC or combustion equipment is suspected of affecting the indoor environment
• A buyer wants additional environmental due diligence before purchasing a property
• Occupants simply want a better understanding of the environmental conditions inside their home or building

Good indoor air quality starts with understanding the building, its occupants, its ventilation, its moisture conditions, and the potential sources of contamination.

Air sampling can provide valuable information, but testing is most useful when it is performed for a reason and interpreted in the context of the entire property.

Identify the concern. Investigate the source. Select the appropriate testing. Correct the underlying condition.

Crystalline silica is a naturally occurring mineral found in many common construction materials, including sand, stone, concrete, mortar, brick, block, tile, ceramics, and engineered stone products.

Silica itself is extremely common. The primary health concern arises when silica-containing materials are cut, ground, drilled, sawed, polished, crushed, demolished, or otherwise disturbed, creating extremely small airborne particles known as respirable crystalline silica (RCS).

These particles are small enough to penetrate deeply into the lungs when inhaled. NIOSH defines respirable crystalline silica as crystalline silica particles that are sufficiently small to reach the gas-exchange region of the lungs. CDC

Crystalline silica may be present in many materials encountered during construction and renovation, including:

• Concrete
• Cement and mortar
• Brick and concrete block
• Natural stone
• Granite
• Quartz
• Engineered stone countertops
• Tile and some ceramic products
• Grout
• Sand
• Rock
• Masonry products
• Certain construction compounds and aggregates

The amount of silica varies significantly from one material to another.

Of particular concern are engineered or artificial stone products, often marketed as quartz countertops, which can contain very high concentrations of crystalline silica. California has experienced a significant number of severe silicosis cases among workers involved in engineered-stone fabrication. California Department of Public Health

A solid concrete slab, stone countertop, or masonry wall does not necessarily create an airborne silica exposure simply because it contains crystalline silica.

The hazard develops when work creates respirable dust.

Activities that can generate respirable crystalline silica include:

• Cutting concrete or masonry
• Grinding concrete
• Drilling into concrete or stone
• Jackhammering
• Saw cutting
• Demolition
• Tuckpointing and mortar grinding
• Cutting brick or block
• Crushing stone or concrete
• Sanding or polishing stone
• Cutting or fabricating countertops
• Abrasive blasting
• Dry sweeping accumulated construction dust

The visible dust cloud produced during construction may contain particles of many different sizes. The most hazardous silica particles can be so small that they are not individually visible to the naked eye.

Silica exposure is commonly thought of as an occupational issue affecting construction workers, miners, masons, and countertop fabricators.

However, uncontrolled renovation or demolition inside an occupied home or building can also distribute silica-containing dust beyond the immediate work area.

For example, cutting, grinding, or demolishing concrete, mortar, tile, stone, or masonry indoors without adequate dust controls may allow particulate debris to migrate onto:

• Floors
• Furniture
• Countertops
• Window sills
• HVAC registers
• Carpeting
• Personal belongings
• Adjacent rooms
• Other occupied portions of the building

Once deposited, fine dust can potentially become airborne again when disturbed by walking, cleaning, vacuuming, moving furniture, or continued construction activity.

This is why proper containment and dust control should be considered before dusty construction begins, not after the dust has already spread.

Repeated or excessive inhalation of respirable crystalline silica can cause serious disease.

NIOSH identifies health effects including:

• Silicosis
• Lung cancer
• Chronic obstructive pulmonary disease (COPD)
• Chronic kidney disease
• Certain autoimmune diseases

Silicosis is a progressive lung disease caused by silica particles producing inflammation and permanent scarring of lung tissue. There is currently no cure for silicosis, although the disease is preventable by controlling exposure. CDC

Symptoms may include coughing, shortness of breath, fatigue, and chest pain, although significant disease can develop before obvious symptoms occur. CDC

Many traditional cases of silicosis developed after years of occupational exposure.

However, extremely high exposures can cause accelerated or acute silicosis in a much shorter period of time.

This has become an especially serious concern among workers fabricating engineered stone countertops. California health officials have documented severe disease, lung transplants, and deaths among relatively young workers exposed during cutting, grinding, and polishing of engineered stone. California Department of Public Health

For this reason, California has adopted enhanced worker protections for certain high-exposure silica operations involving artificial stone and other high-silica materials. CalDIR

Respirable crystalline silica exposure is regulated in the workplace.

California's construction standard, Title 8 Section 1532.3, establishes an Action Level of 25 micrograms per cubic meter of air (25 µg/m³) calculated as an 8-hour time-weighted average.

The occupational Permissible Exposure Limit (PEL) is 50 µg/m³ as an 8-hour time-weighted average. Federal OSHA uses the same exposure limits. OSHA

These are occupational exposure limits, intended for evaluating worker exposure. They should not be interpreted as general residential indoor-air “safe levels.”

The most effective approach is to control the dust at the point where it is generated.

Depending on the task, controls may include:

• Wet cutting or wet drilling
• Integrated water-delivery systems
• Local exhaust ventilation
• Tool-mounted dust collection
• HEPA-filtered vacuum systems
• Proper work-area containment
• Restricting access to dusty work areas
• Appropriate respiratory protection
• Proper cleanup procedures

Cal/OSHA's construction silica standard specifies engineering and work-practice controls for many common construction activities. CalDIR

Simply opening a window or operating an ordinary household fan should not be considered an adequate dust-control strategy for significant silica-generating work.

One particularly important rule concerns cleanup.

Cal/OSHA generally prohibits dry sweeping or dry brushing where it could contribute to employee exposure to respirable crystalline silica unless safer methods are not feasible.

Preferred cleanup methods include HEPA-filtered vacuuming, wet sweeping, or other methods that minimize airborne dust. Compressed air is also restricted for cleaning surfaces or clothing where it could generate silica exposure. CalDIR

This matters because improper cleanup can re-aerosolize dust that had already settled.

Sometimes ERT is contacted after construction has already occurred.

Examples may include:

• Countertop cutting performed indoors without containment
• Concrete grinding
• Tile or masonry demolition
• Saw cutting
• Uncontrolled renovation dust
• Dust migration into adjacent occupied rooms
• Heavy residual dust remaining after construction

In these situations, the first question is usually not simply, “Is there dust?”

The more useful question is:

What was disturbed, where did the dust travel, what contaminants may be present, and does the property need additional professional cleaning or evaluation?

Depending on the circumstances, an investigation may include visual documentation, review of the construction activity, evaluation of dust migration, and targeted laboratory sampling.

Laboratory analysis of settled dust may help determine whether crystalline silica is present in residual construction dust.

However, an important distinction should be understood:

Surface dust sampling is not the same as occupational air-exposure monitoring.

A settled-dust or wipe sample can help document contamination on a surface, but it does not establish what concentration a worker or occupant previously inhaled. OSHA states that bulk or settled-dust samples can confirm the presence of crystalline silica but cannot be used to determine respirable crystalline silica exposure levels. OSHA

Likewise, OSHA does not currently establish a universal acceptable surface-contamination limit for silica dust. Surface results therefore require professional interpretation based on the site conditions, background, construction history, sample location, and intended use of the information. OSHA's general surface-sampling guidance notes that wipe sampling can document contamination but that OSHA standards do not generally establish acceptable surface limits. OSHA

I would absolutely include this section on your website because it protects ERT from suggesting that a silica wipe sample is some kind of regulatory “clearance test” when no universal surface clearance criterion exists.

When the question is whether workers are being exposed to respirable crystalline silica during a task, the appropriate method is generally personal breathing-zone air monitoring using approved respirable sampling equipment and laboratory analysis.

This is different from evaluating residual dust after construction.

Professional air monitoring is used to characterize airborne exposure during the work activity and compare results with applicable occupational exposure limits. OSHA

Engineered stone deserves special attention in California.

Products often marketed as quartz countertops can contain very high levels of crystalline silica. Cutting, grinding, drilling, and polishing these materials can generate extremely high respirable silica concentrations if proper controls are not used.

California has strengthened Section 5204 specifically in response to the silicosis crisis among artificial-stone workers. Certain machining and cleanup activities involving artificial stone are now considered high-exposure trigger tasks requiring enhanced protections. CalDIR

As of September 2026, Cal/OSHA is also considering additional emergency regulations involving fabrication of artificial stone containing more than 1% crystalline silica. That proposal is still undergoing rulemaking and should not yet be described as an adopted prohibition. CalDIR

Silica and asbestos are not the same substance, and they cause disease through different types of mineral particles.

The comparison exists because both hazards can:

• Be present in common construction materials
• Become hazardous when materials are disturbed
• Produce microscopic inhalation hazards
• Cause serious diseases that may take years to develop
• Affect construction workers disproportionately
• Require specialized work practices and exposure controls
• Create significant problems when construction is performed without proper planning

The lesson from both hazards is similar:

Control the material before the dust becomes airborne.

Construction dust should never be dismissed simply because it is common.

If concrete, masonry, mortar, stone, tile, or engineered stone will be cut, ground, drilled, or demolished, appropriate silica controls should be planned before work begins.

If uncontrolled dust has already spread throughout a home or building, determining the source and extent of contamination is the first step toward deciding whether additional professional cleaning or testing is warranted.

Identify the material. Control the dust. Protect the work area. Clean properly. Verify conditions when necessary.

Radon is a naturally occurring radioactive gas produced by the radioactive decay of uranium found naturally in soil, rock, and groundwater.

Radon is colorless, odorless, and tasteless, so its presence cannot be detected without testing.

Outdoors, radon typically becomes diluted in the atmosphere and is generally present at relatively low concentrations. Indoors, however, radon can enter a structure from the soil beneath and around the foundation and accumulate to significantly higher concentrations.

Radon has been found in new homes, older homes, slab-on-grade homes, homes with crawlspaces, homes with basements, tightly sealed homes, and drafty homes. The only way to determine the radon concentration inside a particular building is to test. US EPA

Radon originates primarily from soil gas beneath a structure.

Because indoor air pressure can be slightly lower than the pressure in the soil beneath a building, soil gases can be drawn through openings in the foundation.

Potential entry pathways include:

• Cracks in concrete slabs
• Foundation cracks
• Construction joints
• Gaps around plumbing and utility penetrations
• Openings around pipes
• Crawlspaces
• Sump pits
• Floor drains
• Gaps between slabs and foundation walls
• Hollow block walls
• Other foundation openings

Radon may also occasionally enter through groundwater or be released in very small quantities from certain natural building materials, but soil beneath the building is generally the primary source of elevated residential radon. US EPA

Long-term exposure to elevated radon increases the risk of lung cancer.

EPA estimates that radon exposure contributes to approximately 21,000 lung cancer deaths each year in the United States and identifies radon as the second-leading cause of lung cancer after smoking. US EPA

The risk is substantially greater for people who smoke because tobacco smoke and radon exposure have a combined effect on lung-cancer risk. However, people who have never smoked can also develop radon-related lung cancer. US EPA

Unlike carbon monoxide or some irritating chemicals, radon exposure generally does not cause an immediate odor, headache, dizziness, irritation, or other warning sign.

The concern is long-term cumulative exposure.

EPA states that there is no known safe level of exposure to radon.

The goal should therefore be to keep indoor radon concentrations as low as reasonably achievable.

EPA recommends taking action to reduce radon when the concentration is:

4.0 picocuries per liter (pCi/L) or greater

which is approximately:

150 becquerels per cubic meter (Bq/m³).

EPA also recommends considering radon reduction when concentrations are between 2.0 and 4.0 pCi/L. US EPA

The 4.0 pCi/L level is an action level, not a dividing line between “safe” and “dangerous.”

California is sometimes mistakenly viewed as a state where radon is not a concern.

Elevated radon concentrations have been documented throughout California, and the California Department of Public Health encourages residents to test their homes.

California also maintains statewide and regional radon-potential mapping based on geology and measurement data. However, these maps are intended to identify areas with greater radon potential and should not be used to predict the radon concentration in an individual house. California Department of Public Health

Two homes on the same street—even homes with similar construction—can have significantly different radon concentrations.

Factors influencing indoor radon levels may include:

• Local geology
• Uranium content of the underlying soil or rock
• Soil permeability
• Foundation construction
• Crawlspace or basement conditions
• Building pressure
• HVAC operation
• Ventilation
• Weather conditions
• Occupant behavior

Low regional averages do not eliminate the need to test an individual property.

You cannot see, smell, or taste radon.

Testing is the only way to know the radon concentration inside a home or building. California Department of Public Health

Radon is measured in picocuries per liter of air (pCi/L) in the United States.

Testing devices may include:

• Passive charcoal devices
• Alpha-track detectors
• Electret devices
• Continuous radon monitors
• Other approved measurement technologies

Different methods may be appropriate depending upon whether the purpose is general screening, long-term assessment, post-mitigation verification, or a real-estate transaction.

Short-term radon testing is commonly performed for approximately 2 to 7 days, although some short-term devices can remain deployed for longer periods.

Short-term testing is useful when results are needed relatively quickly, including during a real-estate transaction.

Long-term testing is conducted for more than 90 days and provides a better estimate of the building's average radon concentration over changing seasons and environmental conditions. EPA NEEPA

Because radon levels naturally fluctuate, a single measurement represents conditions occurring during that particular testing period.

Proper testing procedures are critical.

For short-term radon measurements, closed-building conditions are generally required. Windows and exterior doors should remain closed except for normal entry and exit, and equipment that brings significant outdoor air into the building should not be operated contrary to the testing protocol.

For tests lasting less than four days, closed-building conditions should generally be established for at least 12 hours before testing begins and maintained throughout the test. Heating and cooling systems should otherwise be operated normally. EPA NEEPA

The testing device should also remain undisturbed for the entire measurement period.

These controls help produce a representative and defensible result.

Residential radon measurements are generally performed in the lowest level of the home that is suitable for occupancy, depending upon the purpose of the test and applicable measurement protocol.

A basement, lower-level bedroom, family room, office, or other occupiable area may therefore be more appropriate than simply placing the device wherever it is convenient.

Device placement also matters. Testing equipment should not be placed next to exterior doors, open windows, HVAC registers, excessive heat, excessive humidity, or other locations that could interfere with the measurement.

Professional measurements should follow applicable ANSI/AARST radon measurement standards. EPA recognizes these standards for professional radon testing. US EPA

Radon testing can be valuable environmental due diligence when purchasing a home.

California Department of Public Health recommends using a Certified Radon Tester when testing in connection with a real-estate transaction. California Department of Public Health

If a seller has previously tested the property, buyers should consider:

• When the test was conducted
• Where the device was placed
• What testing method was used
• Whether proper testing conditions were maintained
• Whether the home has changed since the test
• Whether a radon mitigation system has subsequently been installed

The presence of elevated radon does not necessarily mean a home should not be purchased. Radon problems can generally be corrected using established mitigation techniques. California Department of Public Health

If testing confirms an elevated radon concentration, a qualified radon mitigation professional can evaluate the building and determine the appropriate reduction method.

For homes constructed over concrete slabs or basements, the most common and generally most reliable method is active sub-slab depressurization.

This typically involves installing one or more suction points beneath the slab and connecting them to piping and an in-line fan. The system creates negative pressure beneath the foundation, captures radon-containing soil gas before it enters the building, and exhausts it safely outdoors. EPA NEEPA

Other techniques may include:

• Sub-membrane depressurization beneath crawlspaces
• Drain-tile suction
• Sump-hole suction
• Block-wall suction
• Sealing significant foundation openings as a supplemental measure
• Other foundation-specific mitigation methods

Simply sealing foundation cracks is generally not considered a reliable standalone radon mitigation strategy.

A radon mitigation system should always be verified after installation.

California CDPH recommends performing a radon measurement after the system has been installed to verify that it is effectively reducing radon concentrations. Homes with mitigation systems should also be periodically retested to confirm continued performance. California Department of Public Health

Radon fans and other system components can eventually fail, so the presence of a mitigation system alone does not prove that current radon levels are acceptable.

Radon levels cannot be reliably predicted by the age of a home, neighborhood, county average, foundation type, or your neighbor's test result.

The only way to know is to test the individual property.

If elevated radon is found, proven methods are available to significantly reduce the concentration.

Test the home. Understand the result. Mitigate when necessary. Verify that the system works.

Electric and magnetic fields—commonly referred to as EMF—are physical fields associated with electricity.

In the United States, homes and buildings operate primarily on 60-hertz (Hz) alternating-current electricity. Whenever electrical wiring or equipment is energized, an electric field may be present. When electrical current flows through wiring or equipment, a magnetic field is produced.

These fields occur naturally and are also produced by virtually every electrical system and device we use.

Common sources include:

• Electrical service panels
• Interior electrical wiring
• Power lines
• Utility transformers
• Electrical substations
• Appliances
• Electric motors
• HVAC equipment
• Computers and electronic equipment
• Chargers and power supplies
• Electric blankets and heating equipment
• Other energized electrical devices

Power-frequency electric and magnetic fields are classified as extremely low frequency (ELF) non-ionizing fields. OSHA identifies 60-Hz fields as being produced by power lines, electrical wiring and electrical equipment. OSHA

Although the terms are frequently grouped together as “EMF,” electric and magnetic fields behave differently.

Electric fields are associated primarily with voltage. An energized wire can produce an electric field even when little or no electrical current is flowing.

Electric fields can be reduced or shielded relatively easily by building materials, vegetation, walls and other objects.

Magnetic fields are produced by electrical current. The greater the current flowing through a conductor, the stronger the magnetic field may be near that source.

Magnetic fields pass more readily through walls, people and most ordinary building materials. However, their strength generally decreases rapidly as distance from the source increases. Cancer.gov

Electromagnetic energy exists across an enormous range of frequencies.

The electromagnetic spectrum includes:

• Extremely low frequency fields
• Radiofrequency fields
• Microwaves
• Infrared
• Visible light
• Ultraviolet radiation
• X-rays
• Gamma rays

An important distinction is whether the radiation is ionizing or non-ionizing.

Ionizing radiation, including X-rays and gamma rays, contains enough energy to directly damage atoms and molecules, including DNA.

Power-frequency electric and magnetic fields are non-ionizing. They do not have sufficient energy to ionize atoms or directly damage DNA in the manner that X-rays or gamma radiation can. Cancer.gov

This is an important distinction that is frequently misunderstood.

Electrical wiring and power lines typically produce extremely low frequency fields at approximately 60 Hz in the United States.

Wireless technologies operate at substantially higher radio frequencies.

Examples of radiofrequency (RF) sources include:

• Wi-Fi routers
• Cell phones
• Cellular towers
• Bluetooth devices
• Smart meters
• Wireless security systems
• Radio and television transmitters

RF is also non-ionizing radiation, but it exists in a different portion of the electromagnetic spectrum and requires different measurement instrumentation than conventional power-frequency electric and magnetic field measurements. NCI distinguishes ELF fields from electrical systems from RF fields produced by wireless communications equipment. Cancer.gov

A meter designed to measure 60-Hz electric and magnetic fields should not be assumed to measure Wi-Fi, cellular or other RF emissions.

Magnetic-field levels can vary significantly throughout a property.

Higher measurements may sometimes be encountered near:

• Electrical service panels
• High-current electrical wiring
• Utility transformers
• Overhead or underground power distribution
• Transmission lines
• Large appliances
• Electric motors
• HVAC equipment
• Electrical equipment rooms
• Certain improperly configured electrical circuits or wiring conditions

A higher reading immediately next to an appliance does not necessarily mean the entire room has the same field level.

Distance matters.

Measurements near many electrical appliances decline dramatically within a relatively short distance from the source. NCI notes that magnetic fields from many household appliances decrease sharply as distance increases. Cancer.gov

People request EMF measurements for many different reasons.

Common situations include:

• A home located near overhead transmission or distribution lines
• A property adjacent to a transformer or substation
• A bedroom near an electrical service panel
• Concern about electrical equipment on the opposite side of a wall
• A new home purchase
• Investigation of unusually elevated magnetic-field readings
• Comparing different areas within a home or building
• Evaluating field strength at beds, desks, workstations or other locations where occupants spend significant time
• Establishing baseline measurements for documentation

An EMF survey can help determine where electric or magnetic fields are present, their measured strength, how readings vary by location and whether an identifiable source appears to be contributing to the measurements.

Electric and magnetic fields are measured separately.

Electric-field strength is commonly measured in:

Volts per meter (V/m)

Magnetic fields may be expressed as:

Milligauss (mG)

or

Microtesla (µT)

For reference:

1 µT = 10 mG

Measurements should be taken systematically because field strength can vary considerably over relatively short distances.

A useful evaluation may include measurements:

• At the suspected source
• At different distances from the source
• At normal occupant locations
• In bedrooms or sleeping areas
• At desks or workstations
• Along walls adjacent to electrical equipment
• Inside and outside the structure when exterior sources are suspected

Measurements taken at only one location may not adequately represent conditions throughout a property.

An EMF measurement is a snapshot of conditions occurring at the time of the survey.

Magnetic-field strength can change as electrical loads change.

For example, readings near a residence may differ depending upon:

• Time of day
• Electrical demand
• Appliances operating
• HVAC operation
• Building occupancy
• Utility loads
• Current flowing through nearby power lines

This is why the source and measurement conditions should be documented when interpreting results.

Power-frequency EMF has been studied for decades.

The scientific evidence does not establish that typical residential electric or magnetic field exposure causes cancer or other disease.

Research has, however, identified a statistical association in some epidemiological studies between relatively high average residential magnetic-field exposure and childhood leukemia.

Pooled studies have reported associations at average magnetic-field exposures around 0.3 to 0.4 microtesla (3 to 4 milligauss) and above. However, these exposures occurred in a relatively small percentage of the populations studied, and researchers have not established that magnetic fields actually caused the increased leukemia incidence. Cancer.gov

Animal studies and laboratory research have generally not provided evidence supporting a causal relationship, and no accepted biological mechanism has been established explaining how low-level ELF magnetic fields would cause cancer. Cancer.gov

The International Agency for Research on Cancer (IARC), part of the World Health Organization, has classified extremely low frequency magnetic fields as “possibly carcinogenic to humans.”

The classification is primarily based on the limited epidemiological evidence involving childhood leukemia.

It does not mean that ELF magnetic fields have been proven to cause cancer.

WHO notes that methodological limitations, the lack of an established biological mechanism and generally negative animal studies prevent the observed association from being considered causal. World Health Organization

This distinction is important because statements that “EMF causes cancer” go beyond what the scientific evidence currently supports.

Not necessarily.

The 3–4 mG range frequently discussed in EMF literature is not a regulatory safety limit.

It originates primarily from epidemiological research in which an association with childhood leukemia was observed among some groups of children with relatively high long-term average residential magnetic-field exposures.

It should not be interpreted as meaning:

Below 3 mG = safe

or

Above 3 mG = dangerous

Science has not established such a threshold.

California has not established a numerical residential exposure standard for power-frequency EMF.

The California Public Utilities Commission states that it has been unable to determine that there is a significant scientifically verifiable relationship between ordinary EMF exposure and adverse health effects. Consequently, the CPUC has not adopted a specific numerical exposure standard. California Public Utilities Commission

Similarly, OSHA states that there is currently no specific OSHA standard for extremely low frequency fields. OSHA

Therefore, an EMF investigation should not be marketed as producing a simple regulatory “pass” or “fail.”

That is another point I would absolutely keep on the ERT website.

A single number without context has limited value.

A useful EMF evaluation considers:

• The type of field being measured
• Measurement units
• Location of the measurement
• Distance from the suspected source
• Duration of occupancy in that location
• Electrical equipment operating at the time
• Background readings elsewhere in the building
• Whether readings change when equipment is switched on or off
• Whether an interior or exterior source appears responsible

The objective is to understand where the field originates and how exposure varies throughout the property, rather than simply searching for the highest number.

When someone wishes to reduce exposure, one of the simplest and most effective measures is often distance.

Because fields from many localized electrical sources decline rapidly as distance increases, moving a bed, desk, chair or other regularly occupied location farther from the source can sometimes substantially reduce exposure. Cancer.gov

Other measures may include:

• Identifying the actual source
• Increasing distance from electrical equipment
• Relocating frequently occupied areas when practical
• Correcting electrical problems when an abnormal wiring condition is identified
• Reconfiguring equipment placement
• Reducing unnecessary proximity to strong localized sources

Any modification to electrical wiring, panels or equipment should be performed by a qualified electrical contractor.

Electric and magnetic fields are a normal consequence of electricity and are present to varying degrees in virtually every home and building.

Finding a measurable field does not automatically mean that a health hazard exists.

A properly performed EMF survey can instead answer practical questions:

Where are the fields strongest?

What appears to be producing them?

How quickly do they decrease with distance?

Are certain normally occupied areas substantially different from background conditions elsewhere in the property?

Can reasonable changes reduce the measured field if the property owner chooses to do so?

Measure the field. Identify the source. 

Understand the conditions. Make informed decisions based on the results.

Volatile Organic Compounds, commonly referred to as VOCs, are a large group of carbon-containing chemicals that can readily evaporate into the air from certain liquids and solids.

VOCs are used in or emitted from thousands of products, including paints, coatings, solvents, adhesives, cleaning products, building materials, furnishings, fuels, pesticides, office products, and personal-care products.

Many VOCs can be present indoors at concentrations higher than those measured outdoors. EPA studies have found concentrations of several common organic pollutants averaging approximately 2 to 5 times higher indoors than outdoors, with substantially higher concentrations possible during activities involving VOC-containing products. US EPA

Common indoor sources include:

• Paints and coatings
• Paint strippers and solvents
• Adhesives and glues
• Flooring materials
• Carpet and carpet adhesives
• Cabinets and composite wood products
• Furniture
• Varnishes and wood finishes
• Cleaning and disinfecting products
• Air fresheners and fragrances
• Pesticides
• Stored gasoline and automotive products
• Hobby and craft products
• Permanent markers
• Printers and office equipment
• Dry-cleaned clothing
• Personal-care products
• Newly manufactured building materials
• Remodeling and construction products

Some VOCs are released primarily while a product is being used, while others may continue to off-gas for days, weeks, months, or longer, depending on the material, chemical, temperature, ventilation, and other conditions. EPA notes that VOCs may be released both during use and, to some degree, while products are stored. US EPA

Recently constructed or remodeled homes can sometimes experience higher VOC concentrations because many new materials may be emitting chemicals at the same time.

Potential sources include:

• New flooring
• Fresh paint
• Cabinets
• Countertops
• Adhesives
• Sealants
• Furniture
• Composite wood
• Insulation
• Caulking
• Finishes
• Cleaning products used after construction

EPA recommends reducing the use of VOC-emitting products in occupied spaces during remodeling and improving ventilation when such materials are used. US EPA

A strong chemical or “new house” odor following remodeling does not automatically mean that a dangerous condition exists, but it may indicate that volatile chemicals are being emitted into the indoor environment.

This is one of the most important things to understand.

VOC is a category, not a single contaminant.

Hundreds of different VOCs may potentially occur indoors, and each chemical has its own:

• Toxicity
• Odor
• Exposure characteristics
• Health effects
• Recommended exposure levels
• Analytical method

Examples may include:

• Benzene
• Toluene
• Xylene
• Ethylbenzene
• Acetone
• Styrene
• Tetrachloroethylene
• Methylene chloride
• Terpenes
• Formaldehyde
• Acetaldehyde

Some VOCs are relatively low in toxicity at typical indoor concentrations, while others can present greater health concerns.

This is why simply stating that “VOCs are present” does not, by itself, determine whether an indoor environment is hazardous. EPA emphasizes that VOC toxicity varies greatly from one compound to another. US EPA

Total Volatile Organic Compounds (TVOC) is a general measurement representing the combined concentration or instrument response from multiple volatile organic chemicals.

TVOC can be useful as a screening tool for comparing rooms, identifying unusual conditions, evaluating trends, or determining whether a strong VOC source may be present.

However, TVOC has limitations.

A high TVOC reading does not necessarily mean the air is dangerous, and a low TVOC reading does not necessarily mean the air is free of potentially important chemicals.

EPA specifically cautions that reducing total VOC concentration does not automatically produce a safer environment because individual VOCs vary significantly in toxicity. US EPA

There are different ways to evaluate VOCs, and the appropriate method depends on the question being asked.

A direct-reading VOC meter can provide real-time screening information and help identify:

• Relative VOC concentrations
• Changes from room to room
• Areas with elevated readings
• Changes over time
• Possible source locations

However, many direct-reading meters do not identify the specific chemical responsible for the reading.

When individual VOC identification or quantification is required, laboratory air sampling may be necessary using an analytical method selected for the compounds of concern.

EPA notes that different VOCs require different sampling and analytical methods and that results cannot be meaningfully interpreted without understanding how the compounds were measured. US EPA

Formaldehyde is one of the better-known indoor VOCs.

Common sources can include:

• Composite wood products
• Particleboard
• Medium-density fiberboard (MDF)
• Cabinets
• Furniture
• Adhesives
• Fabrics
• Certain coatings
• Combustion sources

EPA identifies pressed-wood products containing formaldehyde-based resins as important potential indoor sources. US EPA

Formaldehyde is commonly evaluated separately because it may require a different analytical method from many other VOCs. A general VOC meter should not automatically be assumed to accurately measure formaldehyde. US EPA

That distinction is especially important when investigating a complaint involving new cabinetry, flooring, furniture, or recently remodeled interiors.

Sometimes—but not always.

Many VOCs have recognizable odors, while others may have little or no odor at concentrations of interest.

Likewise, a strong odor does not automatically mean that a dangerous exposure is occurring.

Odor thresholds and health-effect thresholds are not necessarily the same.

Some chemicals can be smelled at extremely low concentrations, while others may present an exposure concern without producing an obvious odor.

Your nose can identify that something is different, but it cannot identify the chemical or determine whether the concentration is safe.

The health effects associated with VOC exposure depend on:

• The specific chemical
• Concentration
• Duration of exposure
• Frequency of exposure
• Route of exposure
• Individual sensitivity

Some VOC exposures may cause:

• Eye irritation
• Nose or throat irritation
• Headaches
• Dizziness
• Nausea
• Fatigue
• Respiratory irritation

Certain VOCs can also affect the liver, kidneys, nervous system, or other organs at sufficient exposures. Some VOCs are known or suspected carcinogens. US EPA

However, EPA also notes that considerably less is known about the health effects associated with many VOC concentrations normally encountered in homes compared with higher occupational exposures. US EPA

Symptoms associated with VOCs are also nonspecific and may have many possible causes unrelated to indoor chemical exposure.

People do not all respond to indoor contaminants in the same way.

Individuals with asthma, respiratory disease, chemical sensitivities, or other underlying conditions may report symptoms at concentrations that do not noticeably affect other occupants.

Children and older adults may also spend more time indoors and therefore may experience different exposure patterns.

Environmental testing can help characterize building conditions but does not diagnose whether a person's symptoms were caused by a particular VOC.

Medical concerns should be evaluated by an appropriate healthcare professional.

There is no single federal indoor-air standard that establishes one universal safe concentration for TVOC in homes.

This is because TVOC represents a mixture of chemicals that can have dramatically different toxicities.

For example, California's Office of Environmental Health Hazard Assessment establishes compound-specific Reference Exposure Levels (RELs) for certain chemicals such as benzene and formaldehyde rather than using one universal TVOC threshold. OEHHA

Therefore, a TVOC number should generally be interpreted as a screening measurement, not as a regulatory pass/fail result.

Product labeling can also be confusing.

A product advertised as:

Low VOC

or

Zero VOC

does not necessarily mean that the product emits no potentially irritating or toxic chemicals.

EPA explains that VOC regulations for many consumer products were developed primarily to reduce outdoor smog-forming emissions. Certain toxic volatile chemicals may not be counted in the regulatory VOC definition used for those labels. US EPA

EPA also cautions that some low-VOC or zero-VOC coatings may still emit other undesirable compounds. US EPA

For indoor air quality, the specific chemical emissions from the product can be more important than the marketing label alone.

California has some of the country's most extensive VOC-control regulations.

The California Air Resources Board regulates VOC content in numerous consumer-product categories in an effort to reduce emissions that contribute to outdoor air pollution and smog. California Air Resources Board

These regulations are important, but compliance with a product VOC limit should not be interpreted as proof that a product cannot affect indoor air quality.

Indoor-air concerns involve what chemicals are actually emitted into the occupied environment and at what concentrations.

The most effective method is usually source control.

Depending on the situation, steps may include:

• Removing or isolating the source
• Increasing outdoor-air ventilation
• Following manufacturer ventilation instructions
• Allowing new products to off-gas before occupancy when practical
• Avoiding unnecessary storage of solvents, fuels, paints, or chemicals indoors
• Selecting lower-emitting building materials
• Controlling indoor temperature and humidity
• Properly exhausting activities that generate VOCs
• Limiting use of fragrances and unnecessary chemical products

EPA identifies source control, ventilation, and air cleaning as the three basic strategies for improving indoor air quality, with source control generally being the most effective. US EPA

A VOC investigation may be useful when:

• Persistent chemical odors are present
• Symptoms appear after entering a particular home or building
• A property has recently been remodeled
• New flooring or cabinetry has been installed
• New furniture was recently introduced
• Paints, coatings, sealants, or adhesives were recently used
• A chemical spill or solvent release may have occurred
• Occupants suspect off-gassing from building materials
• Indoor conditions seem significantly different from outdoor conditions
• An unknown chemical source needs to be investigated
• Baseline indoor-air conditions are desired before or after construction

The appropriate testing method should be chosen based on the suspected source and the question the investigation is intended to answer.

A chemical smell can provide an important clue, but odor alone cannot identify the contaminant or determine exposure.

Likewise, a single TVOC number cannot describe every chemical in the air.

A useful VOC investigation asks:

What changed?

What products or materials are present?

Where are concentrations highest?

Does the suspected source correspond with the measurements?

Is compound-specific laboratory analysis warranted?

Identify the source. Select the correct testing method. Interpret the results in context. Reduce the source when necessary.

Formaldehyde is a colorless, strong-smelling chemical and volatile organic compound (VOC) that can be released into indoor air from many common building materials, furnishings, household products, and combustion sources.

Formaldehyde is widely used in the manufacture of resins, adhesives, and composite wood products. Because these materials are common in residential and commercial construction, formaldehyde can be present in both new and older buildings.

Unlike some contaminants that are only released when a material is disturbed, formaldehyde can be emitted gradually into the air through a process commonly called off-gassing.

Potential indoor sources include:

• Particleboard
• Medium-density fiberboard (MDF)
• Hardwood plywood
• Composite wood products
• Kitchen and bathroom cabinetry
• Furniture
• Shelving and built-in components
• Laminate and engineered flooring
• Adhesives and glues
• Paints, coatings, and finishes
• Certain insulation products
• Fabrics and permanent-press textiles
• Household and cleaning products
• Tobacco smoke
• Gas stoves and other combustion appliances
• Vehicle exhaust entering from attached garages

Composite wood products can be an important source because formaldehyde-containing resins have historically been used to bind wood particles, fibers, or veneers together.

Formaldehyde concerns often arise after new construction, remodeling, or installation of new furnishings and building materials.

A newly renovated home may contain new:

• Cabinets
• Flooring
• Furniture
• Shelving
• Adhesives
• Paints and coatings
• Composite wood products
• Countertop substrates
• Interior finishes

When several new products are installed at the same time, multiple materials may off-gas simultaneously.

Occupants sometimes describe a strong “new house,” “new cabinet,” or chemical odor after remodeling. However, odor alone cannot determine whether formaldehyde is present or whether the concentration is elevated because many other VOCs can produce odors.

Off-gassing is the release of volatile chemicals from a material into the surrounding air.

Formaldehyde emissions are often higher when products are newer and generally decrease as materials age. However, the amount and duration of off-gassing can vary significantly depending on the product and indoor conditions.

Factors that can influence indoor formaldehyde concentrations include:

• Temperature
• Relative humidity
• Ventilation
• Age of the material
• Quantity of emitting materials
• Room size
• Air-exchange rate
• HVAC operation

Higher temperature and humidity can increase formaldehyde emissions from some materials.

The potential effects of formaldehyde exposure depend on the concentration, duration, frequency of exposure, and individual sensitivity.

Exposure to elevated formaldehyde concentrations may cause:

• Eye irritation
• Nose and throat irritation
• Coughing
• Wheezing
• Respiratory irritation
• Headaches
• Nausea
• Skin irritation or sensitization in some individuals

People with asthma or other respiratory conditions may be more sensitive to irritating airborne chemicals.

Formaldehyde has also been extensively studied for long-term health effects and is classified as a known human carcinogen.

This does not mean that any detectable amount of formaldehyde will cause illness. Health risk depends upon the concentration and duration of exposure.

Formaldehyde is technically a volatile organic compound, but it should not automatically be treated the same as a general VOC measurement.

A TVOC meter or general VOC sensor may not accurately measure formaldehyde.

If formaldehyde is specifically suspected, testing should be performed using a method designed to measure formaldehyde rather than assuming that a general VOC reading provides the answer.

Depending on the purpose of the investigation, testing may include:

• Direct-reading formaldehyde screening
• Short-duration measurements
• Time-integrated air sampling
• Laboratory analysis
• Comparison between different rooms
• Indoor and outdoor comparison measurements when appropriate

The appropriate testing method depends on the question being investigated.

Formaldehyde has a recognizable pungent odor at certain concentrations, but odor is not a reliable testing method.

People have different odor sensitivities, and other indoor chemicals can produce similar smells.

A strong chemical odor does not prove that formaldehyde is responsible.

Likewise, the absence of an odor does not prove that formaldehyde is absent.

The only way to determine the actual concentration is to measure it.

California and the federal government have established formaldehyde-emission requirements for certain composite wood products.

Regulated products include materials such as:

• Hardwood plywood
• Particleboard
• Medium-density fiberboard
• Thin MDF

These regulations have significantly reduced formaldehyde emissions from many newer products.

However, a product meeting an emission standard does not necessarily mean that no formaldehyde will be detectable in the indoor air, especially when large quantities of new composite wood products are installed in a relatively enclosed space.

Two similar homes can have very different indoor formaldehyde concentrations.

Differences may result from:

• Amount of composite wood present
• Age and manufacturer of the materials
• Ventilation rate
• Indoor temperature
• Humidity
• Building tightness
• Room volume
• HVAC operation
• Number of new products installed
• Whether windows and doors are frequently opened

This is why the presence of cabinetry, MDF, flooring, or furniture by itself cannot determine whether a formaldehyde problem exists.

A general VOC investigation and a formaldehyde investigation answer different questions.

General VOC testing may be useful when the chemical source is unknown or multiple organic compounds are suspected.

Formaldehyde testing is more appropriate when there is a specific concern involving materials commonly associated with formaldehyde emissions, such as new cabinetry, MDF, composite wood, furniture, or flooring.

In some situations, evaluating both VOCs and formaldehyde provides a more complete picture of indoor chemical conditions.

When elevated formaldehyde is associated with an indoor source, reducing the source and improving ventilation are usually the most effective approaches.

Depending on the circumstances, measures may include:

• Increasing outdoor-air ventilation
• Maintaining moderate indoor temperatures
• Controlling excessive humidity
• Identifying the strongest emitting material
• Removing or replacing a problematic source when warranted
• Allowing new materials to off-gas before occupancy when practical
• Choosing lower-emitting products during future remodeling
• Improving overall building ventilation

Air-cleaning equipment should not automatically be considered a substitute for identifying and controlling the source.

Testing may be appropriate when:

• A home has recently been constructed
• Kitchen or bathroom cabinets were recently installed
• New flooring was installed
• New furniture or composite wood products were introduced
• A persistent chemical odor developed after remodeling
• Occupants notice eye, nose, or throat irritation in a particular building
• Indoor conditions changed following renovation
• Formaldehyde needs to be evaluated separately from general VOCs
• A property owner wants baseline indoor-air information
• A suspected material needs to be evaluated as a possible emission source

Testing is most useful when it is combined with an understanding of what changed in the building, when the materials were installed, where the suspected sources are located, and how the property is ventilated.

A chemical odor does not automatically mean formaldehyde.

A general VOC reading does not necessarily tell you the formaldehyde concentration.

And the presence of MDF, cabinetry, flooring, or composite wood does not by itself establish an indoor air quality problem.

Identify the potential source. Use the appropriate testing method. Interpret the results in the context of the building. Address the source when necessary.

Soil contamination occurs when chemicals, metals, petroleum products, combustion residues, pesticides, asbestos, or other potentially harmful substances are introduced into soil or accumulate above normal background conditions.

Contamination may result from a single event such as a structure fire, fuel spill, or demolition project, or it may develop gradually over many years from past property uses, deteriorated building materials, pesticide applications, industrial activity, vehicle emissions, or contaminated fill.

Soil can appear completely normal while still containing contaminants that cannot be identified by sight, smell, or touch.

The only reliable way to determine whether specific contaminants are present is through representative soil sampling and laboratory analysis.

Potential sources around homes and residential properties may include:

• Structure fires and fire debris
• Demolition of older homes or buildings
• Deteriorated exterior lead-based paint
• Historical paint scraping or sanding
• Petroleum or fuel releases
• Motor oil and automotive fluids
• Pesticides and herbicides
• Termiticides
• Treated lumber
• Burn pits or ash disposal
• Illegal dumping
• Buried construction debris
• Imported fill material
• Former commercial or industrial uses
• Nearby industrial activities
• Naturally occurring metals or minerals
• Asbestos-containing debris or naturally occurring asbestos under certain conditions

Older properties may contain environmental conditions that developed decades before the current owner purchased or occupied the site.

A structure fire can create more than visible building damage.

Burning building materials, furnishings, plastics, paints, wiring, roofing, treated wood, vehicles, household products, and other materials can generate ash and debris containing a variety of contaminants.

Depending on what burned, potential contaminants may include:

• Lead
• Arsenic
• Chromium
• Other metals
• Polycyclic aromatic hydrocarbons (PAHs)
• Petroleum-related compounds
• Semi-volatile organic compounds
• Other combustion byproducts

Fire suppression, debris removal, demolition, excavation, and grading can also redistribute ash and contaminated soil across a property.

A fire does not automatically mean that the soil is hazardous, but targeted testing can help determine whether contaminants remain after cleanup or redevelopment.

Demolition can disturb soil contamination that was previously concentrated around or beneath an older structure.

For example, decades of deteriorating exterior lead-based paint may contribute lead to soil immediately adjacent to a house.

Demolition equipment, grading, excavation, and movement of soil can then redistribute affected material to other areas of the property.

When an older home has been demolished and a new structure is being built, soil screening may provide useful information about environmental conditions remaining at the property before final landscaping, gardening, or long-term residential occupancy.

The appropriate laboratory analysis depends on the history of the property and the suspected source of contamination.

Testing may include:

• Lead and other metals
• Polycyclic aromatic hydrocarbons (PAHs)
• Volatile organic compounds (VOCs)
• Semi-volatile organic compounds (SVOCs)
• Petroleum hydrocarbons
• Pesticides and herbicides
• Polychlorinated biphenyls (PCBs)
• Asbestos in soil or aggregate when appropriate
• Other site-specific contaminants of concern

Not every property should be tested for every possible contaminant.

A better approach is to first determine:

What happened at the property?

What materials or activities may have caused contamination?

Which laboratory analyses are appropriate for those suspected contaminants?

Soil conditions can vary considerably from one part of a property to another.

Contamination may be concentrated:

• Around the former building footprint
• Along exterior drip lines
• Near garages or driveways
• Around former fuel-storage areas
• Beneath burned structures
• Where debris was stored
• Near landscaped areas
• Around former sheds or workshops
• At different depths beneath the surface

For this reason, one random soil sample may not adequately represent an entire property.

A sampling strategy should consider:

• Property history
• Suspected source
• Location of former structures
• Visible staining or debris
• Surface versus subsurface conditions
• Future use of the property
• Number and distribution of samples
• Appropriate laboratory methods

Sampling depth can be important.

Surface soil may be most relevant when evaluating conditions involving:

• Exterior lead-based paint
• Ash or fire debris
• Children's play areas
• Gardening areas
• Direct contact with exposed soil
• Surface spills or deposits

Subsurface soil may be more appropriate when evaluating:

• Buried debris
• Former tanks
• Historical releases
• Excavation areas
• Contamination beneath a demolished structure
• Imported fill
• Suspected deeper contamination

In some investigations, collecting samples at more than one depth can help determine whether contamination is limited to the surface or extends deeper into the soil.

Different contaminants require different sampling and laboratory methods.

The proper:

• Sample container
• Sample volume
• Preservation method
• Holding time
• Laboratory preparation
• Analytical method

can vary depending on what is being tested.

For example, soil collected for volatile organic compounds requires different handling than soil collected for metals or PAHs.

This is why the sampling plan and laboratory analysis should be selected before samples are collected, rather than collecting random soil and deciding later what to test.

A laboratory report identifies which contaminants were detected and their measured concentrations.

A laboratory detection does not automatically mean that the soil is hazardous or requires removal.

Results should be interpreted based on:

• Contaminant concentration
• Sample location
• Sample depth
• Property use
• Potential exposure pathways
• Applicable environmental screening criteria
• Whether the sampling adequately represents the affected area

Environmental agencies use various risk-based screening levels to help determine whether additional evaluation may be appropriate.

A screening level is generally not the same thing as an automatic cleanup level.

Results exceeding an applicable screening criterion may indicate that additional investigation or consultation with an appropriately qualified environmental professional is warranted.

Lead is one of the more common contaminants associated with older residential properties.

Potential sources include:

• Deteriorated exterior lead-based paint
• Historical paint scraping and sanding
• Demolition debris
• Structure fires
• Historical vehicle emissions
• Industrial emissions
• Contaminated fill
• Previous property uses

Lead does not biodegrade and can remain in soil for many years.

Properties containing older structures may therefore have elevated lead concentrations in soil even when the building itself has been renovated or replaced.

Polycyclic aromatic hydrocarbons (PAHs) are a group of chemicals produced during incomplete combustion of materials such as wood, fuels, plastics, and other organic materials.

PAHs may be considered when evaluating properties affected by:

• Structure fires
• Wildfires
• Burn pits
• Petroleum releases
• Vehicle-related contamination
• Certain historical industrial activities

Different PAH compounds have different toxicological significance, which is why laboratories commonly report individual PAHs rather than simply reporting a single generic result.

Petroleum contamination may originate from:

• Gasoline
• Diesel fuel
• Heating oil
• Motor oil
• Vehicle maintenance
• Fuel-storage tanks
• Landscaping equipment
• Commercial or industrial activities

Some petroleum-related chemicals can migrate through soil and, under certain conditions, may also affect groundwater or soil vapor.

More complex petroleum, groundwater, or vapor-intrusion conditions may require evaluation beyond routine residential soil screening.

Past agricultural or landscaping activities can also leave residual chemicals in soil.

Properties that were previously used for:

• Orchards
• Agriculture
• Nurseries
• Pest-control operations
• Commercial landscaping

may have a different environmental history than properties that have always been residential.

Historical pesticide use, including certain compounds no longer commonly used today, may be considered when property history suggests a potential concern.

Asbestos may sometimes be encountered in soil when asbestos-containing building materials have been:

• Demolished
• Buried
• Crushed
• Improperly disposed of
• Mixed with construction debris

Certain areas of California may also contain naturally occurring asbestos associated with specific rock and soil formations.

Testing for asbestos in soil requires specialized sampling and analytical methods and should be performed when asbestos is a reasonable contaminant of concern.

Not every elevated substance in soil was caused by human activity.

Metals and minerals naturally occur in California soils and rock formations, and background concentrations can vary significantly from one geographic area to another.

This is another reason soil laboratory results must be interpreted in context rather than assuming that every detection represents contamination caused by a spill, fire, or previous owner.

Soil contamination screening may be appropriate when:

• A structure was damaged or destroyed by fire
• An older home or building was demolished
• Demolition debris was previously present
• Lead-based exterior paint may have affected surrounding soil
• Petroleum staining or unusual odors are present
• Fuel or chemicals may have been stored or spilled onsite
• Burned or buried debris is discovered
• A property has a history of commercial or industrial use
• Unknown fill material was imported
• Construction may have redistributed affected soil
• A buyer wants additional environmental due diligence
• A property owner plans to create a garden or children's play area near a suspected source
• A specific contaminant is suspected based on property history

This distinction is important.

Targeted Soil Contamination Screening & Laboratory Testing evaluates specific suspected contaminants by collecting representative soil samples from selected areas and submitting them for laboratory analysis.

A Phase I Environmental Site Assessment is a formal environmental due-diligence investigation that includes historical research, regulatory database review, site reconnaissance, and evaluation for recognized environmental conditions.

A Phase II Environmental Site Assessment typically involves more comprehensive subsurface investigation and may include soil, groundwater, soil gas, drilling, monitoring wells, or other environmental media.

ERT provides targeted soil contamination screening and laboratory testing based on specific environmental concerns.

ERT does not represent this service as a Phase I or Phase II Environmental Site Assessment, geotechnical investigation, geological investigation, or comprehensive hazardous-site characterization.

The appropriate next step depends on:

• The contaminant
• Concentration
• Location
• Depth
• Extent of the condition
• Property use
• Potential exposure pathways
• Applicable regulatory requirements

An isolated finding may require a very different response from widespread contamination.

When laboratory findings indicate that additional investigation may be warranted, consultation with an appropriately qualified environmental consultant, Professional Geologist, Professional Engineer, toxicologist, or other specialist may be recommended.

Clean-looking soil may contain contaminants that cannot be seen, smelled, or identified without laboratory testing.

Likewise, unusual-looking or stained soil does not automatically mean that hazardous contamination exists.

A useful soil investigation begins with the history of the property and the suspected source.

Understand what happened. Identify the contaminants of concern. Develop an appropriate sampling plan. Use qualified laboratory analysis. Interpret the results in context.