Understanding Smoke Damage

Smoke is material released into the air by a fire: a changing mixture of gases, tiny solid particles and liquid droplets. Some of it is visible. Much of it is too small to see.

Heat breaks down the material that is burning. Incomplete combustion creates soot and other pollutants. Certain vapors can cool and become particles. Other substances already present in the burned material can be carried in airborne ash or particles.

Even a forest fire burning only natural vegetation can produce harmful smoke. Wood smoke contains fine particles and pollutants such as benzene, formaldehyde, acrolein and polycyclic aromatic hydrocarbons, often called PAHs. A chemical does not have to have been added to a tree for that chemical to be produced when the tree burns.

Sources: EPA: Wildfire Smoke, A Complex Mixture · EPA: Frequent Questions about Wood-Burning Appliances

Trees, homes and vehicles do not produce identical smoke. The fuel, temperature, oxygen supply and conditions as smoke travels all affect the mixture.

Possible contaminants are reasons to investigate, not proof that every listed substance is in every smoke-affected home.

Sources: EPA: Wildland Fire Research, What's in Smoke? · EPA: Wildfires and Indoor Air Quality

Rising hot air carries smoke upward, and wind moves it away from the fire. Fine particles can travel with that air and reach buildings outside the burned area.

1. Carried through the air

   Gases and particles move with a smoke plume.

2. Drawn into the building

   Open doors and windows, outdoor-air intakes, and small gaps around the building can admit polluted air.

3. Left in the living space

   Particles may remain airborne or deposit on surfaces. Some smoke chemicals attach to surfaces or enter materials.

Closing windows helps reduce entry, but ordinary homes are not airtight. A home's exposure depends on how much smoke reaches it and how air moves through the building. Smoke damage therefore deserves consideration even when walls, windows and the roof appear intact.

Sources: EPA: Wildfires and Indoor Air Quality · NIST / Science Advances: The Persistence of Smoke VOCs Indoors

People can breathe smoke pollutants while spending time indoors. The health concern includes both the amount in the air and how long someone is exposed.

If someone has severe trouble breathing or chest pain, seek emergency medical help. A property inspection is not a substitute for medical care.

Sources: EPA: Wildfire Smoke, A Complex Mixture · EPA: Wildland Fires and Public Health Effects · EPA: Wood Smoke and Your Health

The word matters because it describes a serious hazard. Smoke can contain carcinogens, and EPA warns that fire-affected sites may also contain cancer-causing chemicals among the hazards left behind.

A hazard is not the same as a prediction for an individual family. Cancer risk depends on the substance, the amount and duration of exposure, and individual factors. Finding a carcinogen does not mean that cancer will develop. Finding smoke residue does not, by itself, establish a person's exposure or cancer risk.

Research on repeated and longer-term wildfire smoke exposure is developing. EPA describes initial studies reporting cancer associations with cumulative exposure over multiple years, while emphasizing limits in the evidence and in how exposure is measured. Those findings should not be presented as proof that one smoke event, or residue in one home, will cause cancer.

The practical response is to take potential exposure seriously, reduce it, and use an assessment that addresses the conditions in the property.

Sources: National Cancer Institute: Environmental Carcinogens and Cancer Risk · EPA: Protect Yourself from Ash · EPA: Durations of Smoke Exposure

The visible cloud and the contamination left indoors are different parts of the problem.

Smell and appearance are useful observations, but they cannot identify every chemical or measure its concentration. Removing an odor also does not document that a particular contaminant has been removed.

Sources: EPA: Protect Yourself from Ash · NIST / Science Advances: The Persistence of Smoke VOCs Indoors · EPA: Carbon Monoxide Poisoning, Protect Your Family and Yourself

For a smoke-affected property, discuss the fire history, visible residue, odors, affected rooms and ventilation with a qualified environmental or industrial hygiene professional. Ask whether targeted sampling would help guide cleanup or evaluate the work afterward.

• What contaminants are being investigated, and why are they relevant to this fire?
• Will the samples examine air, settled dust, surfaces or materials? What does each sample tell us?
• Which locations will be sampled, and how were they chosen?
• What laboratory methods and detection limits will be used?
• What comparison or clearance criteria will be used, and what are their limitations?
• How will the findings guide cleaning, replacement or follow-up testing?

Results apply to the substances, locations and conditions that were evaluated. A particle monitor, odor check or single surface sample cannot certify that a whole house is free of every carcinogen. Ask for a written report that explains the findings and what was not evaluated.

Professional assistance is especially important when there is structural damage, suspected hazardous material, an affected HVAC system or a cleanup beyond what you can safely manage. Follow local public-health and re-entry guidance.

Sources: EPA: Protect Yourself from Ash

During an active fire, evacuation orders and local safety instructions come first. Once authorities allow return, avoid unnecessary contact with ash and prevent it from being tracked into clean areas.

• Keep children away from ash-contaminated areas. People at higher risk should not take part in ash cleanup.
• Avoid dry sweeping, leaf blowers and other actions that send settled ash back into the air. Use appropriate protective equipment and cleanup methods for the material and conditions.
• Use suitable particle filtration when the building and equipment are safe to use. Ventilate when outdoor conditions permit. Filtration does not replace removal of deposited contamination.
• Avoid ozone, hydroxyl generators and other oxidizers used to remove or neutralize smoke odors; EPA advises against products that add these chemicals to the air.

If your home has been affected, get a clear assessment of the conditions before deciding what to clean, what to replace and how to evaluate the results.

Sources: EPA: Protect Yourself from Ash · EPA: Wildfires and Indoor Air Quality