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Wildfire smoke, air quality and your health

Learn about wildfire smoke events, the effects of wildfire smoke on your health, and how to protect yourself.

About wildfire smoke events

Communities across Canada regularly experience wildfire smoke events. This is expected to continue as Canada is warming much faster than the rest of the world, providing ideal conditions for more frequent and longer wildfires. Wildfire season typically runs from early April to late October. As wildfires burn through forests and grasslands, they produce dense smoke.

It is difficult to predict:

  • when fires will occur
  • how big they will be
  • how much smoke they will generate
  • what direction the smoke will travel

Wildfire smoke may be carried hundreds or thousands of kilometres from the fire zone. This means smoke from other parts of the world can impact communities in Canada.

Wildfire smoke and pollution levels

Smoke from wildfires can be a major source of air pollution for people in Canada.

Wildfire smoke is a complex mixture of gases, particles and water vapour that contains pollutants such as:

  • sulphur dioxide
  • nitrogen dioxide
  • carbon monoxide
  • volatile organic compounds
  • fine particulate matter (PM2.5)

This pollution contains fine particles (not visible to the human eye) that get deep into our lungs and bloodstream. These can sometimes lead to serious health effects, including death.

There’s no evidence of a safe level of exposure for some of these pollutants. This means that smoke can impact your health even at very low levels. As smoke levels increase, your health risks increase. Air pollution may be present even when you can’t see or smell smoke.

Wildfire smoke events and extreme heat

In Canada, wildfire season can happen at the same time as periods of extreme heat. The most intense fires often occur when the weather is the hottest. This means you may be exposed to wildfire smoke and extreme heat at the same time.

How to protect your health when experiencing wildfire smoke and extreme heat together

Air quality health index and wildfire smoke

The air quality health index (AQHI) is a tool used to tell you about:

  • the health risks associated with local air pollution
  • actions you can take to protect your health

How the AQHI is calculated

The AQHI is calculated using the concentrations of 3 air pollutants that are harmful to health:

  • ozone
  • nitrogen dioxide
  • fine particulate matter (PM2.5)

These pollutants are considered the best indicators of the health risks associated with the mix of outdoor air pollutants in Canadian communities.

The AQHI is presented on a scale of 1 to 10+ with 4 health risk categories:

  • 1 to 3 = ‘low’ health risk
  • 4 to 6 = ‘moderate’ health risk
  • 7 to 10 = ‘high’ health risk
  • Above 10 = ‘very high’ health risk

During smoky conditions the fine particulate matter (PM2.5) concentrations can override the health risks of the combined 3 pollutants. The AQHI is then calculated and reported hourly using only the PM2.5 to help people in Canada better respond to wildfire smoke events. During these events, a rapid change in the AQHI’s forecast values will occur and a special air quality advisory may be issued. These values can be followed:

Once the smoke moves away from the area, the AQHI will be calculated using the 3 pollutants and become more stable.

AQHI 10+ during wildfire smoke events

In Canada, an AQHI value of 10+ is typically due to very high levels of fine particulate matter (PM2.5) from wildfire smoke.

An AQHI of 10+ indicates a very high health risk due to air pollution and/or wildfire smoke. When the AQHI reaches 10+, air pollution and health risks may continue to increase but the AQHI will not increase any further. This is the highest health risk category on the AQHI scale. When the air is polluted enough to cause an AQHI of 10+, everyone’s health is at risk and it is important to:

  • take precautions to protect your health
  • follow the advice of local health officials

Learn more about air quality and how the weather affects wildfire smoke.

Symptoms of wildfire smoke exposure

Milder and more common symptoms of smoke exposure include:

  • headaches
  • a mild cough
  • production of phlegm
  • sore and watery eyes
  • nose, throat and sinus irritation

You can typically manage these symptoms without medical intervention.

More serious but less common symptoms of smoke exposure include:

  • dizziness
  • chest pains
  • severe cough
  • shortness of breath
  • wheezing (including asthma attacks)
  • heart palpitations (irregular heart beat)

If you have any of these symptoms, talk to a health care provider or seek urgent medical attention.

Less commonly, exposure to wildfire smoke can lead to:

  • stroke
  • heart attack
  • premature death

If you think you are having a medical emergency, dial 9-1-1 and seek immediate medical care.

Who is most at risk of the effects of wildfire smoke

Some people are at higher risk of health problems when exposed to wildfire smoke. This includes:

  • seniors
  • pregnant people
  • infants and young children
  • people who work outdoors
  • people involved in strenuous outdoor exercise
  • people with an existing illness or chronic health conditions, such as:
    • cancer
    • diabetes
    • mental illness
    • lung or heart conditions

During heavy smoke conditions, everyone is at risk regardless of their age or health.

Preparing for wildfire smoke events

You can do many things to prepare yourself and your home for wildfire smoke events.

Checklist for wildfire smoke season preparedness

  • Are you or is someone in your family at risk for wildfire smoke health effects?
  • Do you have an adequate supply of medications?
  • Do you have an adequate supply of food and water?
  • Do you have spare filters for the air filtration unit (a high efficiency heat ventilation air conditioning (HVAC) system or a portable air cleaner) in your home?
  • Do you know where you can go to take a break from the smoke?
  • Do you know where to find information about local air quality conditions?
  • Do you know the emergency number for your local health authority?

Medical preparedness

If you, or members of your family, are in 1 or more of the at-risk groups and are in a region where wildfire smoke affects air quality, be prepared by:

  • speaking with a doctor or health care provider about developing a management plan for wildfire smoke events
  • maintaining a supply of necessary medications at home and always carrying these medications with you during wildfire season. Work with your health care provider to create a plan on what to do in case your medications are unable to stabilize your condition.

Protecting your indoor air

It’s important that the air you breathe inside your home is clean, especially if you have to stay inside due to wildfire events. You can prepare your home by finding ways to keep the wildfire smoke out and to keep indoor air clean.

Keep wildfire smoke out

Prevent wildfire smoke from entering your home by:

  • properly sealing windows and doors, and keeping them closed when the temperature is comfortable
  • installing a high-quality air filter to remove particulate matter from the incoming air, in homes with forced air ventilation
  • learning how to use the recirculation settings on your HVAC system

Keep indoor air clean and safe

Protect the air in your home by:

  • reducing sources of indoor air pollution
  • installing the best air quality air filter that your ventilation system can handle based on manufacturers’ recommendations
  • ensuring you have at least one functioning carbon monoxide alarm in your home
  • having air conditioning and humidification/dehumidification capabilities present (maintain humidity levels between 30 and 50%)
  • using a certified portable air cleaner with a HEPA filter to remove smoke from indoor air

To find more information on protecting your indoor air when your outdoor air is poor, visit:

Protecting your health from wildfire smoke

The best way to protect your health is to reduce your exposure to wildfire smoke.

Use care when spending time outdoors during a wildfire smoke event

Limit outdoor activities and strenuous physical activities as much as possible. If you have difficulty breathing, reduce your activities or stop altogether.

If you or members of your family spend time outdoors, learn how to check the local air quality conditions to determine whether it’s safe to be outdoors. Pay attention to:

Check the AQHI for air quality conditions in your community. Look for breaks in the smoke to find opportunities to go outdoors. Reschedule your outdoor activities for a time when conditions are better.

If smoke is present for more than a few days, stay active when you can. Try finding a place with clean air to exercise indoors, for instance at the gym, the community centre or at home.

If you need to work outdoors, check with your provincial or territorial occupational health and safety organization or your local health authority. They can provide guidance on how to work safely outdoors during wildfire smoke events.

Have a plan for limiting exposure to wildfire smoke if you will be caring for children or participating in any outdoor events.

Ensure access to cool, clean air

Use your air conditioner. If available, set your HVAC system to recirculation mode when the outdoor air is poor, and bring in fresh air when the outdoor air has improved.

Limit the use of exhaust fans when you’re not cooking.

If you can’t maintain cool, clean air inside your home during a wildfire smoke event, be aware of locations in your community where you can find clean air and take a break from the smoke.

Safe places that typically have air conditioning and filtered air include:

Contact your local health or emergency authorities to find the most up-to-date information about publicly accessible locations.

Wildfire smoke events and extreme heat can happen at the same time. During these times, if you can’t spend time in cooler and cleaner air, try these 3 protective measures:

  • Drink lots of water, even if you don’t feel thirsty.
  • Limit exercise and exertion that makes you sweat or breathe hard.
  • Stay out of the sun, take cool showers, spray yourself with a water bottle, or wear an article of damp clothing to cool your body.

Other tips to protect your health during wildfire smoke events

You can reduce the impacts of wildfire smoke on your health if you know when wildfire smoke is expected to affect your community.

Find reliable information about wildfire conditions

Take care of your mental health: It’s not unusual to feel anxious, stressed out, sad or isolated during a smoke event. Eating well, getting enough sleep, exercising indoors and staying in contact with friends can help. Anyone who is having trouble coping with symptoms of stress, anxiety or depression should seek help from a health care provider. Remember, a wildfire smoke event may last a long time, but it will eventually end. Sharing positive outlooks and attitudes will help you get through it.

You can access free mental health supports here:

Leave the area, if possible: If you’re vulnerable to the health effects of wildfire smoke and smoke levels in your community are high, evaluate whether or not it’s possible to temporarily re-locate to an area with cleaner air.

Evacuate, if necessary: If your community is threatened by an approaching wildfire, your local health or emergency authorities will provide direction. Be prepared to evacuate at any time. If told to evacuate, do so.

What to do in a wildfire emergency

Stay safe in your vehicle: Keep vehicle windows closed and set the ventilation system to recirculate. Make sure you change your cabin air filters regularly.

Chemical safety and air quality in your car and garage

Stay hydrated: Drink plenty of cool liquids, especially water, to decrease your risk of dehydration and help your body cope with the smoke. If a fire occurs close to your water well, use an alternate source of water, such as bottled water, until you can have your well water tested. Don’t use contaminated water for any purpose, including:

  • drinking
  • making ice
  • giving to pets
  • washing dishes
  • brushing your teeth
  • washing your hands
  • making baby formula

Be Well Aware: Information for private well owners

Care for others: Check in on others who are in your care or live nearby who may be more vulnerable to wildfire smoke. Frequently check in on neighbours, friends and older family members, especially those who are chronically ill.

Resources for creating cleaner air spaces

Community-based cleaner air spaces require planning to:

  • ensure that the building is suitable for housing large numbers of people
  • protect the health of its occupants

If you are responsible for providing clean, cool air during a wildfire, you can refer to:

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