Wildfire Smoke and Indoor Air Quality

Protect your Home this Fire Season

Published on August 3rd, 2021

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Satellite data reveals that smoke from wildfires can drift far from the blaze affecting air quality over thousands of kilometers. When the smoke reaches urban areas, it can interact with existing pollutants to produce elevated ozone levels. Inhaling ozone can irritate airways and cause coughing, congestion, headaches and sore eyes in healthy people. It can also worsen the symptoms of bronchitis, emphysema and asthma.

Those health issues are concerning, but the major threat of wildfire smoke, according to the U.S. Environmental Protection Agency, is the fine particulate within the haze. Microscopic pieces of ash smaller than 2.5 microns can enter our eyes and air passages. Some of the ash comes from burnt buildings that contained paint and plastics. The Journal of the American Heart Association confirms there is a connection between wildfire smoke particles and cardiac arrest. Research by the association also found there is an increase in emergency-department hospital visits from exposure to these fine smoke particles.

This summer, wildfires in Canada have produced a brownish-gray haze that shifts on the winds, intermittently blanketing communities. According to a Canadian Press article on July 27, 2021, these fires have been large enough to generate their own weather systems. The intense heat of fires burning through drought-ravaged areas and whipped up by high winds, create pyrocumulonimbus firestorms. 

Michael Fromm, a meteorologist with the United States Naval Research Laboratory, based in Washington, D.C., studied pyrocumulonimbus firestorms that occurred this summer (2021) in British Columbia, Alberta, Saskatchewan, Manitoba and Ontario.

In the Canadian Press article, Fromm explained that “a pyrocumulonimbus storm usually begins with a smouldering fire, which feeds on the surrounding air turning active and creating a thermal bubble. That creates a convection column that generates more energy and turns the fire hotter and larger.”

Although wildlife is trapped in the smoke, people have the option to take shelter indoors. The EmergencyInfoBC website (https://www.emergencyinfobc.gov.bc.ca), by the Government of British Columbia, suggests these steps to preserve the quality of indoor air:

  • Keep windows and doors closed as much as possible. 
  • If you use an air conditioner, be sure to keep the fresh-air intake closed
  • Use a wet mop on floors to remove particulate 
  • Avoid activities that create smoke or other particles indoors, including:
    • Smoking cigarettes, pipes, and cigars
    • Using gas, propane or wood-burning stoves and furnaces
    • Spraying aerosol products
    • Frying or broiling food
    • Burning candles or incense
    • Vacuuming, unless you use a vacuum with a HEPA filter

A portable air filter can help to purify your indoor environment but be cautious. Oddly enough, an interaction between the mechanism, the filter material and existing indoor pollution, can produce harmful ozone. Even if a filter claims to produce ‘safe levels of ozone,’ this gas can build up over time, especially when the windows and doors are closed against wildfire smoke.

Before you purchase an air filter, check the product details and search for independent product information from reputable online sources such the provincial and federal governments, the Environmental Protection Agency, and Consumer Reports. 

A good air filter will reduce smoke particulate as well as other common elements of indoor air: pollen, mold, pet dander and volatile organic compounds (VOCs) such as formaldehyde, which is released from paint, flooring, furniture, and cleaning products. VOCs can irritate eyes and respiratory systems, but over the years these chemicals also damage the lungs, liver, kidney, and nervous system.

For added protection indoors and out, you may wish to use an N95 mask, which filters particles as small as approximately 0.3 microns. N95 masks are made with a material that produces electrostatic absorption, so that particles are drawn to the fiber and trapped, instead of just passing through. If you need to exercise, do so indoors at a moderate pace and ideally use an N95 mask.

Until we can reduce the incidence of wildfire, these measures can improve your indoor air quality. 



Alam, Hina. “Wildfires in Canada are creating their own weather systems, experts say.” Canadian Press. July 27, 2021.

Journal of the American Heart Association. “Out of Hospital Cardiac Arrests and Wildfire Related Particulate Matter During 2015–2017 California Wildfires.” April 15, 2020.

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