What to Know About Keeping Wildfire Smoke Out of Your Home

As smoke from wildfires in Canada rolls down into the United States, the air quality in the Northeast, Midwest and mid-Atlantic has plummeted.

Over 75 million people in the U.S. are under air quality alerts and are being advised to avoid the outdoors as much as possible.

The easiest way to avoid inhaling hazardous air is to stay indoors and wear a high-quality mask whenever you’re outside.

But, in certain buildings, such as those constructed decades ago, smoky air can seep inside leaky windows and doors, bringing harmful particles into the home.

"There are two general ways to decrease your exposure to wildfire smoke – breathe less or breathe cleaner air. Breathing cleaner air is more easily achieved – though the strategy for achieving this goal varies depending on where you are or how your home is constructed," Mike Van Dyke, PhD, an associate professor in the Department of Environmental and Occupational Health at the Colorado School of Public Health at the University of Colorado Anschutz Medical Campus, told Healthline.

Here's how to keep your indoor air clean if you’re under an air quality alert right now:

Wildfire smoke contains a mix of gases and tiny particles, called PM 2.5, that can make anyone sick in high quantities.

Van Dyke says these particles are small enough to travel deep into the lungs and be absorbed into the bloodstream.

"Exposure to these particles can cause respiratory irritation which can exacerbate asthma symptoms as well as cause inflammation and oxidative stress which could lead to more severe respiratory and cardiovascular effects," Van Dyke said.

Studies have shown that exposure to dense wildfire smoke is associated with increases in hospital visits for respiratory and cardiovascular issues.

The risk is greatest among individuals with preexisting respiratory and heart conditions, older adults, young children, and pregnant people.

"People should try and keep wildfire smoke out of their homes because wildfire smoke contains lot of harmful chemical pollution," says Shahir Masri, ScD, an associate specialist in air pollution exposure assessment & epidemiology, Department of Environmental & Occupational Health at the University of California, Irvine Program in Public Health.

The best way to keep your indoor air clean is to make sure your windows and doors are shut.

Doing so will prevent ash and smoke from getting inside your home.

"This is important because it helps keep particulate matter (PM) pollution, such as PM 2.5, out of your home, and therefore reduces your exposure to harmful air pollution," says Masri.

A high-quality air purifier, such as those that contain HEPA filters, can be very effective at keeping your inside air clean.

According to Masri, some can reduce air pollution by half or more.

You can find air cleaner recommendations from the Asthma & Allergy Foundation of America here.

The Environmental Protection Agency (EPA) suggests running your air cleaner on the highest setting.

Experts advise against using ionic purifiers as they can do more harm than good.

"They can create ozone (another air pollutant), and are often more expensive," says Masri.

If you can't find an affordable air cleaner, you can create your own. Here's the EPA's guide for using a DIY air cleaner.

If you have forced air or a central heating and cooling system, keeping the air on will help recirculate the air and filter out the harmful particles in the wildfire smoke, according to Van Dyke.

The effectiveness depends on what type of air system you have in your home — "the higher the ‘MERV’ rating, the better the filtration will be," says Van Dyke.

If you have an HVAC system, set it to recirculate mode, and if you have a window unit, turn off the outdoor air intake damper.

If you cannot turn off the outdoor air intake damper, turn the entire AC unit off as you don't want it pulling smoky air into your home.

According to Van Dyke, many window air conditioner units filter the indoor air as it is cooled and will provide some reduction in indoor wildfire smoke.

Finally, don't use outdoor mounted evaporative coolers if you have one as these can bring large quantities of outdoor air into the home.

Be aware of similar settings when driving a car.

"If closed, and running your car AC, you can achieve reductions in PM-related air pollution by 50-80% during a wildfire, making it potentially more effective than an at-home purifier," says Masri.

A less obvious tip is to not vacuum when the air is harmful outside.

"Vacuuming generates a large amount of airborne dust which requires air flow and dilution to dissipate," says Van Dyke.

It's best to vacuum when you can open the windows.

The EPA also recommends limiting the use of gas, propane and wood-burning stoves and furnaces when the air quality is poor.

Try not to use aerosol products, avoid smoking cigarettes, skip frying or broiling food, and ditch the candles or incense.

All of these activities can create more fine particles and worsen your indoor air quality.

Finally, a high-quality face mask, such as an N95 mask or KN95 respirator, can prevent you from breathing in pollutants.

In order to work properly, the mask should be secured tightly to the face.

These masks "should be strongly considered during long periods of time outdoors when the Air Quality Index exceeds 150 or if you have pre-existing respiratory or cardiovascular issues," says Van Dyke.

It's worth noting that fabric face coverings and surgical face masks offer little protection against wildfire smoke, Van Dyke added.

When the hazardous smoke blows away and the air is clean again, you’ll want to freshen your indoor air.

Take advantage of days where the AQI is 50 or lower and open the windows, says Van Dyke.

"Opening your doors and windows to clean outdoor air will very quickly remove the PM and gaseous air pollutants," Masri says.

As smoke from wildfires in Canada rolls down into the United States, the air quality in the Northeast, Midwest and mid-Atlantic has plummeted. In cities with air quality alerts, health officials are urging people to avoid going outside, but even indoor air can be hazardous. By shutting your windows and doors, using high-quality air cleaners, changing your AC setting, you can keep your indoor air clean on hazy days.