Improve indoor air quality from wildfire smoke during COVID-19

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Officials warn us to stay indoors when air quality is poor due to heavy smoke from wildfires. Reduced exposure to smoke helps protect our lungs, heart, eyes, nose, throat and immune systems. Staying indoors, if possible, can be one of the best ways to protect against the potentially harmful effects of wildfire smoke. What steps can we take to minimize potentially serious health impacts from wildfire smoke that might seep into our homes?

There are several ways outdoor air can enter your home. These include:

  • Open windows and doors
  • Devices such as bathroom or kitchen fans that vent to the outdoors
  • Heating, ventilation and air conditioning (HVAC) systems with a fresh air intake.

Wildfire smoke could affect your indoor air quality (IAQ) differently depending on the proximity of the fire and the smoke density. The smoke can also infiltrate through small openings, joints, and cracks, as well as around closed windows and doors.

Smoke from burning homes, commercial buildings, trucks, automobiles and gas stations contains harmful gases, chemicals and fine particulate matter. When they merge with forest fire smoke that increases exposure risk. Air quality alerts such as the Air Quality Index (AQI), focus on six main components: Nitrogen dioxide, sulfur dioxide, ozone, carbon monoxide, lead and particulate matter (PM2.5 and PM10). In a wildfire, the major contributors to smoke are fine particulate matter. Of particular concern are the smallest of these particulates, known as PM2.5. These small particles are invisible to the eye, but are so small they can reach the deepest portion of your lungs and be absorbed into the body. Larger particles, called PM10, are large enough that they are trapped high up in the lungs and typically coughed out, yet can still cause irritation.

Respiratory symptoms such as dry cough, sore throat, and difficulty breathing are common to both wildfire smoke exposure and COVID-19. More serious complications can occur for everyone as the AQI rating intensity increases and can be especially harmful for those who are seriously ill. Seek advice from a medical professional if conditions persist.

At-risk populations sensitive to wildfire smoke exposure include:

  • Children younger than 18; Adults age 65 years or older
  • Pregnant women
  • People with chronic health conditions such as heart or lung disease, asthma or diabetes
  • Outdoor workers
  • People of low socioeconomic status, including those who are homeless and with limited access to medical care.

Also vulnerable to risk in this pandemic are people with compromised immune systems as well as those with or who have recovered from COVID-19.

If there is an active fire in your area, follow your local news for information and recommendations from your local emergency manager. Emergency managers may also maintain web pages or other communications systems that you may want to follow or join so you can get automatic updates. Conditions can change quickly, so you should always be prepared to evacuate if necessary.

You can get outdoor air quality updates from the website, or Oregon Air Quality Map website. When the Air Quality Index indicates smoke levels are unhealthy, take steps that will help improve or maintain the indoor air quality in your home or if necessary, focus on a smaller area for a clean room. Air quality web sites or apps may also report on the level of harmful contaminants in the smoke with a PM2.5 rating scale.

Setting up a clean room at home can help reduce exposure to dangerous or unhealthy wildfire smoke while indoors. Without a central HVAC system or multiple portable air cleaners, it can be hard to improve the air quality in all areas of the home. Focusing the steps below in a smaller area can maximize best air quality with the resources available. The clean room should be big enough to fit everyone in your household and comfortable to spend time in.

Avoid leaving the house, but when necessary, remember to practice six-feet physical distancing and wear a mask.Cloth masks that can provide protection from COVID-19 will not protect you from wildfire smoke. Look for respirators (masks) marked NIOSH with N95 or P100. These can be found online or in drugstores, hardware, or home repair stores. Masks with vents should be taped shut, or a cloth mask placed over the vent. Frontline healthcare workers use them during the pandemic so they may be in short supply.

Improve your indoor air quality

Start with simple no-cost steps, first. Additional benefits come from purchasing a portable air cleaner with High Efficiency Particulate Air (HEPA) filter, upgrading the HVAC system with best quality high-efficiency filters or making a low-cost portable air cleaner (do not leave unattended).

Prevent smoke from entering

Close windows and doors in the room, but don’t block or tamper with the exits. Only use an exhaust fan or range hood for short periods.

Avoid activities that create smoke or other particles indoors

  • 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.

Keep calm

Learn more about how to stress less to improve your resiliency in a disaster.

Minimize exercising

This can help reduce exposure to any contaminants that may be present. Reducing your activity levels are the best ways to reduce the amount of pollution you breathe into your lungs.

Drink plenty of water

This helps minimize and reduce symptoms of scratchy throat and coughing. Dust or mop surfaces with a damp cloth as needed to keep settled particles from getting back into the air.

Minimize bringing smoke particles inside

Individuals returning home from activities with prolonged exposure to wild fire smoke should consider wiping shoes or boots on a wet towel before entering the home. Set up a plan so they can carefully remove and bag all clothing and take a shower before dressing. Launder clothing immediately or as soon as practical.

Stay cool

Run fans, window air conditioners, or central air conditioning. If your window air conditioner or HVAC system has a fresh air option, turn it off or close the intake.

Filter the air in the room

Use a commercial portable air cleaner that is the right size for the room. Use high-efficiency HEPA air cleaning filters, if available. Avoid using an air cleaner that works by generating ozone, which will increase the pollution in your home. Run the portable air cleaner continuously on the highest fan setting if you can. Room air cleaners will provide the most protection when placed where people spend the most time, such as a bedroom. A good portable air cleaner placed in a bedroom may be particularly helpful to a person with asthma or COPD. For retired or homebound individuals, the portable room air cleaner should be set up in whichever room is used the most.

To maximize air cleaner effectiveness:

  • Operate it continuously, or as often as possible.
  • Use the highest fan speed and make sure the airflow to the air cleaner is not obstructed.
  • Keep outside doors and windows closed to prevent additional particles from entering the room.

During a wildfire smoke event, commercial portable air cleaners fitted with high-efficiency filters may reduce indoor particle concentrations by as much as 45%.

If you have central HVAC, you can also install or upgrade a high-efficiency filter (MERV 13 or higher) in the system. Run the system’s fan as often as possible to get the most out of the filter.

A do-it-yourself (DIY) box fan air cleaner is made by attaching a high-efficiency filter (MERV 14 or higher) to a box fan with a bungee cord or tape. Arrows on the filter need to point towards the box fan on the air intake side. There is some limited positive evidence to support its use. However, there are concerns that the box fan motor may overheat when operated with a filter attached. Use the device with caution and do not to operate it unattended or when sleeping to avoid any potential fire or electrical hazard.

See these video instructions, “How to make your own clean air fan” from Washington Department of Ecology. Triangle-shaped versions may be more stable in a rambunctious household, but may not be as effective since PM2.5 can travel through cardboard used to bridge the gap between filters.

See the Indoor Air Filtration fact sheet and EPA’s Guide to Air Cleaners in the Home for more information.

People and pets will all benefit from precautionary steps to improve indoor air quality in your home while you wait for wildfire smoke to clear. Assume that homes that are in Level 3 Evacuation Zones are heavily contaminated. Homeowners should follow directions of local emergency management before reentering. Personal protective equipment or commercial cleaning may be required.


AirNow. Environmental Protection Agency (EPA) and Partners.

Create a Clean Room to Protect Indoor Air Quality during a Wildfire. Environmental Protection Agency (EPA)

Frequently asked questions about wildfire smoke and public health. Oregon Health Authority.

Extremely High Levels of PM2.5: Steps to Reduce Your Exposure. AirNow, Environmental Protection Agency (EPA).

Health Tips for Wildfire Smoke. Deschutes County Health Services.

How to Make your own Clean Air Fan. Washington Department of Ecology.

National Ambient Air Quality Standards. Environmental Protection Agency (EPA).

Oregon Air Quality Map. Oregon Department of Environmental Quality.

Particulate Matter (PM) Pollution. Environmental Protection Agency (EPA).

Wildfire Smoke and COVID-19: FAQs. United States Department of Agriculture, Northwest Wildfire Coordinating Group.

Wildfire Smoke and your Health. Oregon Health Authority.

Wildfire Smoke Guide In Sections - Chapters 1-3. sponsored by Environmental Protection Agency and Partners. h

Wildfires and Indoor Air Quality. Environmental Protection Agency (EPA).


Diana Rohlman, PhD. Assistant Professor (Sr. Res), College of Public Health and Human Sciences, Oregon State University.

Theresa C. Mayhew, MA, Family & Consumer Sciences Resource Educator, Cornell Cooperative Extension

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