Reducing wood smoke and protecting indoor air quality is more important than ever during the COVID-19 pandemic

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Tuesday, February 23, 2021
Melanie Langille

Wintertime in Canada sees many of us spending more time indoors. Perhaps even more so this year due to COVID restrictions. Amidst the second waves of COVID-19, we are reminded of the effects the environment has on our health.

It is widely recognized that the winter season offers prime opportunity for viral infections such as cold, flu, and now SARS CoV2 to transmit between people. This is due in part to the body’s response to cold, dry air, and our habits of spending additional time indoors. Gatherings that may be held outside in the summer are generally held indoors during cooler months. And now COVID restrictions have many of us at home during work and leisure hours more than ever before.

The harsh Canadian winter weather encourages us to seal up our homes and buildings to keep out the cold. And while this may be a good idea from an energy efficiency perspective, it is important to be mindful that this also reduces ventilation in the home. As such, any pollutants in the air can tend to accumulate. This is important to keep in mind when doing home renovations to increase efficiency too.

Residential Wood Burning

Many Canadians still rely on wood burning either as a primary source of heat or as a backup in the event of power outages. But the smoke from burning wood has serious health consequences. People with existing respiratory problems (such as asthma, chronic obstructive pulmonary disease (COPD), or COVID-19) may suffer more serious symptoms; otherwise healthy individuals can also be affected.

Woodstoves are an unhealthy way to heat a home. Wood smoke releases many chemicals and pollutants, the most concerning of which are:

  • PM5: Particulate matter less than 2.5 microns in diameter can be inhaled deep into the lungs and physically and biochemically damage the tissues.
  • Carbon Monoxide (CO) reduces the blood’s ability to supply oxygen to the body’s tissues that can cause stress to the heart and lead to unconsciousness and death at very high levels.
  • Nitrogen Oxides (NOx) can lower our resistance to lung infections and irritate the upper airway
  • Sulphur Dioxide (SO2) causes airway inflammation.
  • Formaldehyde is a known carcinogen and can also trigger asthma attacks.
  • Black Carbon is a major component of soot and can exacerbate climate change by way of its higher ability to absorb solar energy.
  • Polycyclic aromatic Hydrocarbons (PAHs) are known carcinogens.

Fine Particulate Matter

While the composition of wood smoke can vary, PM2.5 is always present and has been associated with adverse health effects at any level of exposure. According to Environment Canada, residential wood burning represents the third highest source of anthropogenic PM2.5 emissions(road dust and construction emissions are also significant source of PM2.5. , after road dust and construction emissions. PM2.5 Using woodstoves as a source of residential heating is therefore not recommended due to negative health impacts from exposure to contaminants.

Reducing Exposure to Residential Wood Smoke

During the COVID-19 pandemic and it being a serious respiratory disease, lung health is never been more important. Reducing your exposure to wood smoke is one way to protect lung health and thus can reduce risks to harm.

Burning wood at home could also lead to higher risks of exposure from opening the stove to stoke the fire or by adding firewood, as well as through leaks and cracks in faulty or poorly-maintained stoves.

Removal of the source of exposure is best and it can be done by investing in and installing an energy efficient heat pump in the home. Heat pumps reduce the need for you to use your wood stove. However, if wood is the only source of heat consider these measures:

  • burning only clean, dry wood; never plastics or household garbage;
  • ventilating enough to keep the fire burning briskly, not smoldering;
  • cleaning, maintaining, and having the stove inspected regularly to ensure it is performing optimally;
  • installing a cleaner burning emission-certified woodstove.

On some occasions it may be difficult to reduce external sources of the smoke, such as a neighbour’s burning practices or a wildfire in your area. However, there are still steps that can reduce exposure: keep windows and doors closed as much as possible; maintain home furnace to operate at an optimal level and with clean filters. The home heating system may have the capacity of lowering the “fresh” air intake that can reduce the amount of outdoor air being circulated in the home.

Potable air cleaners can also be an effective option to reduce indoor air pollution. There are many different types of air cleaners on the market in Canada, but not all have proven health claims. The BC Centre for Disease Control offers a useful fact sheet to guide Canadians in selecting a portable air cleaner that is suitable to remove wood smoke pollutants from indoor air.

Collaboration Is Needed to Reduce Wood Smoke in Canada

Wood is a primary or secondary heating source for many Canadians. Biomass burning accounts for over 6% of all energy consumption in Canada[i] and residential wood burning remains the primary contributor to wintertime PM2.5. With nearly 15,000 premature deaths in Canada each year linked to air pollution[ii], reducing wood smoke can save lives.

Despite actions to reduce emissions (which include updating the Canadian emission standards for woodstoves, Canadian Council of Ministers of the Environment’s Code of Practice for Residential Wood Burning Appliances, and Environment Canada’s Model Municipal Bylaw for Regulating Wood Burning Appliances), implementation has been limited. To date, municipal by-laws regulating residential wood smoke have been put into place only in Montreal and some communities in British Columbia.

The New Brunswick Lung Association convened a National Wood Stove Smoke Summit in 2019 to identify barriers in reducing woodstove use in Canada. Based on the summit, a working group has been developing a strategy document to overcome these barriers. The strategy document will be provided to Health Canada in March 2021.  

There has been much emphasis on “building back better” following the pandemic and a transition to a low carbon economy. Wood burning has been touted as a climate-friendly alternative to fossil fuel use. Trees are renewable, and carbon is sequestered in the trees while they are growing. However, wood burning is not as good a climate change solution as many think. It takes years for trees to absorb CO­2 and only a few months to burn it, releasing that CO2. Burning wood creates black carbon, which can worsen rather than mitigate effects of climate change. As outlined here, the environmental effects from burning wood on human health cannot be ignored.

Key Messages

  • It is important to reduce indoor air pollution, especially during the pandemic as we spend more time at home.
  • Wood smoke pollutes both the outdoor and indoor air, and is a serious health concern.
  • Those who rely on wood as their primary heat source can reduce the amount of smoke produces with safer burning practices.
  • Wood smoke from neighbours’ burning or wildfires can be reduced in the home using mechanical filtration.
  • More needs to be done to protect Canadians from wood smoke.
  • Wood should not be considered a viable renewable energy source due to the health risks of wood smoke.


Author Bio

Melanie Langille is the Vice President of the New Brunswick Lung Association and serves on CSA’s technical subcommittee reviewing wood burning appliance emission standards.

I have no commercial interests or funding that presents a conflict of interest for this article.


Works cited:

[i] Government of Canada. 2020 Bioenergy and Bioproducts..

[ii] Government of Canada. 2021. Health Effects of Air Pollution.