The Effects of Wildfire Smoke on Indoor Air Quality

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Wildfire Smoke and the Effects on Indoor Air Quality

The recent Marshall Fire in Boulder County, CO (January 2022) left devastation the magnitude of a war zone. The damage was HEARTBREAKING when I was driving through the area last week. All that is left of many homes are chimneys, skeletons of lawn furniture, and burnt-out wrecks of cars.

It was amazing that only two people lost their lives. Current numbers are that 1,084 residence structures were destroyed and 149 were damaged. The estimated cost of this event is over $500 million.

What is not captured in these numbers is the immediate impact to resident’s health during the event due to wildfire smoke. There is also a longer-term concern regarding indoor air quality in the homes still standing.

Short Term Effects

During a wildfire event, people caught in the direct path of the smoke end up inhaling a toxic mix of particulates and pollutants. It isn't just trees and vegetation burning, but also treated wood used in construction, plastic, fiberglass, oil, gas, propane, and thousands of other substances that our homes and furniture are made of. The burning of these substances releases Volatile Organic Compounds (VOCs) into the air. Short-term effects can be as minor as eye and respiratory tract irritation to more severe health issues such as asthma flare-ups and heart failure.

"The biggest health threat from smoke is from fine particles. These microscopic particles can penetrate deep into your lungs. They can cause various health problems, from burning eyes and a runny nose to aggravated chronic heart and lung diseases. Exposure to particle pollution is even linked to premature death." – EPA Website.

Particulates found in wildfire smoke are measured in microns. These particulates can be inhaled into the deepest recesses of the lungs and cause wheezing, coughing, chest discomfort, and shortness of breath. It can cause a runny nose, congestion, and eye irritation. People with allergies and asthma often experience a worsening of their symptoms.

Particulates from wildfire smoke can drift for miles. Colorado has been affected by smoke from wildfires as far away as California, Oregon, Washington, and even Canada. A fire doesn't have to be nearby to negatively affect your health.

Wildfire Smoke Effects on Your Home

No home is airtight. Windows and doors never seal 100% when closed. Bathroom and kitchen vents provide a conduit for air to move between the inside and outside.

In situations like the Marshall Fire, winds were 100+ mph. Those winds pushed the fire quickly from house to house. It also forced the wildfire smoke just as fast and further from the center of the fire.

Fast-moving winds accelerated the the Marshall fire in Boulder, Colorado. Smoke and debris is found in homes miles away from the fire.

(Photo courtesy of the Denver Post.)

With such a mighty wind, homes that were downwind of the fire have been contaminated with particulates and pollution, even if it isn't readily visible. Here is a picture of the windowsill of a home located less than a mile from the fire.

Wildfire smoke debris in a windowsill.

You can see the large particulates and soot that came in through the bottom of the window frame. These are only the visible particles. Much of wildfire smoke contains fine particles smaller than can be seen with your eyes.

The day after the fire, it snowed in Colorado. The amount of debris and particulates on the ground is visible in the following picture.

Wildfire debris from the Marshal fire found in fresh-fallen snow.

Notice how the shoveled snow is peppered with debris and ash from the fire. If these two pictures demonstrate what you can see entering your home and surrounding your home from the fires, imagine what you can't see! Contaminants can build up in your home without your knowledge and cause respiratory problems.

Biological Components of Wildfires

With the increased frequency and intensity of wildfires, a new research field called pyroaerobiology has emerged. A fire ecologist at the University of Idaho in Moscow, Leda Kobziar, and students at the University of Florida in Gainesville conducted their first wildfire air sample study in 2015. Since then, she has been working with the U.S. Forest Services as part of its Fire and Smoke Model Evaluation Experiment. Kobziar and her team have identified living bacteria and fungi in every sample of smoke.

In research conducted in Utah, over 100 different fungi not in the air before the fire showed up were found in the wildfire smoke. Examples of microbes that are spread by wildfire smoke are Aspergillus, a mold that can cause respiratory problems, and Valley Fever, an infection common in the Southwest and California caused by the fungus Coccidioides.

A local microbiologist at the University of Colorado Boulder, Noah Fierer, investigates what microbes are present in our air. His team is sampling indoor and outdoor air across Colorado and will compare the baseline numbers to what is present in wildfire smoke. The end goal is to determine what type of microbes are carried by smoke and the potential impact on our health.

How to Minimize the Impact of Wildfire Smoke in Your Home

Smoke conditions vary significantly during a wildfire. When thinking about minimizing the impact of wildfire smoke in your home, consider what to do during a fire and after a fire.

During a Fire

Adjust your activities based on local Air Quality Reports:

  1. If the smoke or the air quality in your town is bad, limit your activities outside. The Air Quality Index can be found on many weather apps or at
  2. Don't do yard work or let the kids play outside
  3. Wear an N-95 or a P-100 respirator to protect your lungs from fine particles if you must go out. Ensure that they fit properly and are used correctly.

Secure your home's air quality:

  1. Keep your windows and doors closed and run your air conditioner
  2. Avoid using anything that burns, such as fireplaces, gas logs, gas stoves, candles, and essential oil diffusers. With wildfire smoke contaminating the air, you do not need other things contributing to poor indoor air quality
  3. Avoid vacuuming; this stirs up particles in your home
  4. Use a portable air cleaner with a HEPA filter to pull contaminants out of the air

After a Fire

After a wildfire, your home may have a smoky smell, or you may notice debris around the windows and door frames. There are often contaminates from a wildfire that you can't see, fine particulates, or even microbes that can affect your health. There are several things you can do to improve your indoor air quality after a wildfire:

Portable Air Cleaner: A portable air cleaner sized appropriately for your rooms and utilizing a HEPA filter can significantly reduce the particulate levels in your home. Do not use an air cleaner that generates ozone, which adds to the pollution levels inside.

Change Furnace Filter and Have Ducts Cleaned: Furnace filters can help filter out some contaminants, but the heavier debris can build up in your ductwork. It is good practice to clean your ducts regularly. Still, it becomes even more critical after a bad wildfire smoke event.

Deep Clean Your Home: As seen in the picture above, debris can accumulate on surfaces after a wildfire. Dusting hard surfaces and vacuuming soft surfaces such as sofas, chairs, and mattresses can go a long way to removing particulates from your home. Be sure to use a vacuum with a HEPA filter, though!

Check Your Attic Insulation: Wildfire smoke can infiltrate the attic via the roof vents. The debris is then deposited on your insulation and can then make its way into your home. In some cases, the insulation must be removed (by a licensed contractor) and replaced.

Debris from the Marshall wildfire in Boulder found in attic home insulation.

Have Your Home and Ducts Disinfected: To destroy contaminants and smoke odors, have your home and ducts treated with a disinfectant. This will break down any pollutants, VOCs, and microbes that have worked their way into your home from the wildfire.

Need Help? Contact Us!

Contact us for your wildfire odor and contaminant remediation needs at or 720.212.9466. We can also test the air quality in your home to determine the level of small and large particulates, VOCs, Formaldehyde, and Carbon Monoxide. We provide mold testing and inspection services, mold remediation, indoor air quality testing, disinfecting, and odor control services.

Trust Bactronix of Colorado to take care of your disinfecting and mold remediation. Call us today to schedule an assessment!


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