Health precautions during wildfires

A changing climate is expected to have many impacts, one of which is an increased risk of wildfires. Smoke generated from wildfires is a mixture of gases and fine particles from burning trees and other plant materials. It can significantly affect air quality, both locally and at a distance.

Wildfire smoke can make the air dangerous to breathe.  

Wildfire smoke contains harmful pollutants such as fine particulate matter (PM2.5), carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs). Exposure to these pollutants can lead to lung and heart issues, especially among vulnerable populations such as young children, seniors, pregnant women and people with health conditions.

Exposure to wildfire smoke can cause a variety of health effects, from mild irritation to more serious impacts for people with existing health conditions. Symptoms may include:

• eye irritation – itchy, red, watery eyes
• nose and sinus irritation - itchy, runny or congested nose
• throat irritation - scratchy or sore throat
• general symptoms such as headaches, fatigue or dizziness
• new or worsening respiratory symptoms such as coughing, wheezing or shortness of breath

If you have heart or lung disease, smoke might make your symptoms worse. People with heart disease might experience chest pain, rapid heartbeat or shortness of breath.

When smoke levels are high enough, even healthy people may notice some of these effects. 

People at higher risk

While everyone can experience symptoms, people who are most at risk from poor outdoor air quality include:

• older adults
• infants and children
• pregnant people
• people who work or exercise strenuously outdoors
• people who smoke
• those with pre-existing health conditions, including cancer, diabetes, mental illness and lung or heart conditions

What you can do to protect yourself

When poor air quality is expected, or you can see or smell/taste smoke in the air, you should do the following:

• monitor the Air Quality Health Index (AQHI)  and other advisories before planning outdoor activity
• limit the amount of time you spend outdoors - reduce or reschedule outdoor strenuous work or exercise
• stay indoors and take measures to maintain indoor air quality
• monitor your symptoms closely (especially if you must spend significant time outdoors) - act if you notice symptoms of poor air quality
• prioritize keeping cool if severe heat occurs along with poor air quality
• use the air conditioning on the recirculation setting, when possible, to avoid having outside air enter the home
• consider wearing a mask

A proper mask can be one of the tools in your toolbox to protect yourself from poor air quality. However, there are a few important things to know about mask use during wildfires:

• masks should be certified N95 or equivalent respirator (KN95 or KF94) as those are the most effective to filter out small particles - homemade masks (such as scarves, bananas) or dust masks that are available for purchase at hardware stores would not be adequate
• fit is important - make sure the mask is well-fitting and properly worn
• while a proper mask can help reduce your exposure to very small particles, it doesn't protect against other contaminants included in wildfire smoke such as gases

When to seek medical attention

Contact 811 for medical advice if symptoms get worse.

Seek urgent medical care or call 911 if you experience severe or worsening shortness of breath, chest pain, dizziness, or other concerning symptoms. 

Cleaner air spaces are designated indoor environments-such as libraries, community centres, schools, or malls-where measures are put in place to ensure air quality is improved to provide temporary relief from wildfire smoke. Cleaner air spaces help people stay safe when the air outside is smoky.

Steps for keeping air clean inside community buildings

Use air filtration. Use heating, ventilation and air conditioning (HVAC) systems capable of filtering very small particles from smoke (ie PM2.5). Filters should have a Minimum Efficiency Reporting Value (MERV) of 13 or higher. Use portable HEPA air cleaners where HVAC upgrades are not possible. Make sure that appropriate equipment is selected according to the size of the air space being filtered.

Design entryways effectively. Include staging areas to minimize direct exposure to outdoor air during entry and exit.

Train personnel. Assign facility managers who understand HVAC operations and can respond to changing air quality conditions.

Close windows and doors. Keep smoke from getting inside. If possible, seal windows to prevent outside air from getting in.

Limit activities that affect indoor air quality. Avoid candles and smoking, as well as strong chemicals. For buildings with a kitchen or cafeteria, cooking and using exhaust fans should be avoided, or if required should be limited to periods when outdoor smoke levels are low. Gas stoves can deteriorate air quality if exhaust fans are not running, and their operation may increase the amount of outdoor air that enters the building through gaps in the envelope.

Make spaces cool and comfortable. Keep the space below 26°C and not too humid.

Have back-up power available. This ensures that air systems continue to work during power outages.

Plan for occupancy. Determine maximum safe occupancy in advance.

Check the air. Use air quality monitors if possible. If air quality monitoring is conducted, target conditions are as follows:

• PM2.5 should be kept as low as possible. Indoor levels should be lower than outdoor levels
• carbon monoxide (CO) should be kept below 10 ppm
• carbon dioxide (CO2) should be kept below 1000 ppm
• temperature should be kept below 26 °C
• relative humidity should be kept between 35 and 50%
• other pollutants such as nitrogen oxides (NOx), polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs), should also be kept as low as possible

Maintain filters. Since dirty filters don’t function effectively, have extra replacements on hand and plan for frequent changes.

Set ventilation modes. Switch between recirculation and fresh air intake based on outdoor conditions.

Use proper cleaning protocols. Use wet cloths or mops to avoid stirring up dust. Limit the use of chemicals.

Steps for keeping air clean inside

Seal your home to keep smoke from getting inside. Close all windows and doors tightly. When possible, use door sweeps, weather stripping, caulking or foam strips to seal gaps around windows.

Designate a room in your home to use as a cleaner air space. Choose a room with few windows and doors. Keep the windows and doors closed and minimize entry and exit. Avoid activities that worsen air quality (e.g., vacuuming, burning candles, frying food).

Use air filtration. Use a portable air cleaner with a HEPA filter rated for the size of your room. If you have a central HVAC system, install filters with a MERV rating of 13 or higher, if compatible. Keep extra filters on hand and replace/change filters regularly during smoke events to maintain effectiveness.

Monitor outside air quality. Use apps or websites to check the Air Quality Health Index (AQHI) 

Keep space cool and comfortable:

• indoor temperature should be kept below 26°C
• maintain relative humidity between 35–50%
• use air conditioning if available and required but ensure that it recirculates indoor air rather than drawing in outdoor air

Limit indoor pollutant sources. Avoid smoking indoors or burning candles. Do not use wood burning stoves or fireplace and limit the use of gas stove and exhaust fans unless outdoor air quality improves.

Prepare for possible power outages. Have a backup power source (battery-powered air cleaner or generator placed away from air intakes). Keep extra batteries on hand.

Use proper cleaning protocols. Use wet cloths or mops to avoid stirring up dust when cleaning. Avoid vacuuming without a HEPA filter unless your vacuum exhausts to the outside. Limit the use of chemicals products.

Commercially available portable air cleaners with HEPA filters can help to significantly improve indoor air quality during wildfire events by helping to remove small particles from the air; however, they can be expensive or hard to find. In that case, homeowners may choose to make their own air cleaner using box fans and furnace filters.

Research suggests that properly constructed homemade air cleaners can be very effective at removing small particles from the air. Studies have shown them to be effective in homes over short periods, but there is no data on long-term use. They also DO NOT remove other indoor air pollutants such as volatile organic compounds (VOCs), carbon monoxide (CO), or carbon dioxide (CO2).

When planning to create and use a “do it yourself” (DIY) air cleaner:

• use a clean, newer (2021 or later) box fan with a safety fuse and multiple speed options
• use newer model fans with thermal protection to reduce fire risk
• look for marks from recognized certifying organizations such as UL, CSA, or Intertek ETL
• use a high-efficiency filter, preferably MERV 13 (FPR 10 or MPR 1500-1900) or higher

Materials needed:

• box fan (20-inch preferred)
• one or two 20” x 20” High-efficiency furnace filter MERV
• 13 or higher (1” depth is adequate)
• duct tape
• markers
• cardboard
• scissors or a box cutter

To get started

Plug in the fan and test airflow direction.

Use a marker to draw an arrow from the back (the side that draws air in) to the front (the side that blows air out), in order to clearly indicate the direction of air flow across the fan.

Option 1 - single box fan filter

1. Make a shroud using cardboard and/or duct tape (See instruction on making a shroud below)
2. Align the filter against the back of the fan (the side that draws air in), making sure that the filter’s air flow direction is in the same direction as the fan
3. Using duct tape, attach the filter onto the fan ensuring there are no air spaces

Option 2 – double box fan filter

1. Make a shroud using cardboard and/or duct tape (See instructions below)
2. Cut two triangles out of cardboard with each side measuring 21” and each angle measuring 60 degrees. Add duct tape as needed to close all gaps around the edges and corners of the cardboard.
3. Tape the two filters together along one side, make sure the arrows on the edges of the two filters are pointing forward.
4. Tape the tops of the two filters to one triangle, and the bottoms to the other triangle. Make sure the arrows on the edges of the filters point to the inside of the triangle, where the fan will go.
5. Tape both filters and triangles to the back of the box fan, ensuring there are no air spaces. 

NOTE: It is very important to align the air flow arrow on the filter with the air flow of the fan.

How to make a shroud

The shroud stops air from being recaptured into the fan from the corners, which would reduce its effectiveness.

Using duct tape:

1. Use duct tape around the front of the fan to create a border
2. Measure 2 ½ inches from the outer edge of the fan on each side. Multiple strips of tape will be needed
3. Measure 5 ½ inches from the outer edge on each corner and place duct tape to form an octagonal shape

Using cardboard:

1. Cut a piece of cardboard the same size as the front of your fan
2. Measure and mark a 2 ½ inch border around the outer edges and 5 ½ inches at each corner
3. Align the marking to make an octagonal shape
4. Remove the center using scissors or a box cutter
5. Using duct tape, attach the cardboard shroud to the front of the fan (the side that blows air) ensuring not to have any openings

Using the air cleaner

• Place the air cleaner in a central location in the room
• Run the fan on low or medium speed for quieter operation and better filtration
• Close windows and doors to prevent smoke infiltration

Safety precautions

• Never leave the fan unattended while running
• Do not block the back or front of the fan – keep it away from walls, curtains, furniture, etc
• Avoid placing the air cleaner near flammable materials
• Use only certified filters and fans that are in good working conditions
• Do not use the fan if the filter is clogged or damaged and replace filters when visibly dirty or after heavy use
• Ensure the fan is not overheating
• If poor air quality is expected over long periods, consider more permanent measures to improve indoor air quality, such as purchasing a commercial air cleaner or upgrading the Heating, Ventilation, and Air Conditioning (HVAC) system