Hundreds of wildfires originating in Canada descended over the midwest and eastern U.S. this June. While some regions in the west and in the south of the country are more accustomed to smoke, orange skies and ash are a new sight for others. 

As climate change progresses and global temperatures rise, scientists warn that the size, frequency, and severity of wildfires will only increase. According to the Environmental Defense Fund, the average wildfire season in the western U.S. is already three months longer than it was a few decades ago, and the Canadian government accurately predicted higher-than-normal fire activity this fire season due to long-range forecasts of warm temperatures coupled with the ongoing drought. 

Besides destruction to infrastructure and the natural world, wildfire smoke also poses a major health risk. It contains gaseous pollutants like carbon monoxide, as well as extremely small particles that easily enter lungs and airways. Many of these particles are so small, they can be seen only with an electron microscope. Exposure to pollutants may cause airways to become inflamed, constricted, or otherwise irritated, and cause other physical symptoms like itchy or stinging eyes, a scratchy throat, headaches, runny noses, chest tightness, fatigue, and coughing, or aggravate chronic cardiovascular conditions like heart disease. Some groups are especially at risk, including children, pregnant people, adults over 65, and those with pre-existing lung conditions like asthma and COPD. 

If wildfire smoke begins to impact your community, there are a few things you can do to keep yourself healthy and safe. 

Monitor Air Quality

The severity of polluted air isn’t always visible, so stay informed by checking the Air Quality Index at AirNow.gov, which is run by the U.S. Environmental Protection Agency (EPA) and provides air quality data by region. The AQI measures the density of five major air pollutants: carbon monoxide, ground-level ozone, nitrogen dioxide, particulates, and sulfur dioxide. During the wildfire season, the measurement called PM 2.5 (which stands for particulate matter) is especially important. This number indicates the concentration of particles in the atmosphere that are smaller than 2.5 micrometers — like those from soot, ash, and dust — which are easy to inhale.

Air quality is determined by the pollutant with the highest concentration at a given moment (which is usually particulates during wildfires), and is given a rating from 0-500: 0-50 (green) indicates little or no risk; 51-100 (yellow) means that air quality is acceptable, but there is some risk for people who are sensitive; 101-150 (orange) indicates that sensitive groups may experience health effects, but the general public is less likely to be impacted; 151-200 (red) is considered unhealthy, and the general public may have health effects; above 201-300 is unhealthy for everyone, especially people with heart and lung disease; and 301-500 is very hazardous for all people. 

Air quality websites and apps can help you track AQI, like IQAir, AirNow, and NOAA’s fire weather outlook.. 

Close Windows and Doors 

Shutting off your home from outside air is one of the most effective ways to keep indoor air quality safe. Close all doors and windows to prevent particulates from entering the house. If windows or doors are drafty or have gaps around the edges, use painter’s tape or tuck towels (preferably damp ones) to create a seal. Consider installing weather stripping around these gaps to protect against future smoke as well. 

Avoid Going Outdoors

Stay inside as much as possible during smokey conditions. Work from home if you can, or drive/take public transportation to work instead of walking to minimize time outdoors. If you must go outdoors, avoid strenuous activities like exercising or mowing the lawn. In general — even apart from wildfire smoke — it’s unsafe to exercise outdoors if the AQI is higher than 150. 

Wear a Mask or Respirator

If you have to go outside, wear a suitable mask or respirator to protect yourself from harmful gases and airborne particles. A scarf or cloth mask — even a surgical mask — won’t offer much protection, so use a close-fitting respirator mask that completely covers your nose and mouth. Respirators differ from other masks in that they are meant to filter out very small airborne particles. N95s and KN95s are respirator masks — which you might already have on hand as a method of COVID protection — and while they’re very effective at protecting wearers from airborne particulates (as much as 95%), they don’t protect much against gases like carbon monoxide that are present in the smoke. If you must go outside (especially if your job requires you to work outdoors for a long period of time), a NIOSH (National Institute for Occupational Safety and Health) Approved respirator is the best option for protection.

Use Air Conditioning 

It’s safe to run air conditioners during smoky weather, as long as you take a few precautions. Especially in the summer with all of the windows and doors closed, it can get very hot. If you don’t have air conditioning, seek a community center or household that does. 

For central HVAC systems, change the filter as often as recommended by the manufacturer, and close the fresh/outdoor air intake (which might allow smoke to get into your house). Some of these systems allow for high-efficiency air filters. If so, install one that’s classified as MERV 13 or higher. Most window air conditioners have an outdoor air damper near the top, which prevents rain or snow from entering. Close this before running to block any outside air from being sucked in. Portable air conditioners with hoses work slightly differently and might pull in smoke, so check the details for your specific model before turning it on. 

Use Air Purifiers 

Keep indoor air clean with a high-efficiency particulate air (HEPA) purifier. Air purifiers can reduce particles indoors by as much as 85%, according to the EPA. They can, however, be very expensive, ranging in price from $50 to $1,000 for a single unit. 

If you only purchase one machine, choose one room as a “clean room” to set it up in, paying attention to the space requirements listed on the product. Consumer Reports recommends getting a purifier that’s marketed for larger spaces of at least 350 square feet, claiming they operate better. Close all windows and doors — including those that lead to other rooms — and sleep there if possible. 

Ideally, get an air purifier in advance to have on hand for smoky weather, as stores might sell out as air quality worsens. Consumer Reports and Wirecutter have recommendations for the best models, and guidelines for indoor air filtration are available on AirNow. 

Keep the Indoors Clean, and Avoid Smoke- or Particle-Producing Activities 

Maintain high air quality inside even without an air purifier by avoiding certain activities. Refrain from using aerosol sprays and candles, or gas, propane, and wood-burning stoves. Avoid cooking if you can, as frying and broiling foods can create smoke or particles that get trapped indoors. 

When you go outdoors into polluted air, particles can quickly settle on your body and clothing. Change clothes and shower when you come in from outside to avoid spreading the particles around your home. Vacuuming can disturb pollutants and release them into the air, so it’s better to wipe surfaces and floors with damp cloth.

Drink Water

Staying well hydrated is important for kidney and liver function, which help remove toxins from the body and reduce inflammation. Drinking water also reduces some physical symptoms from smoke exposure, like coughing and scratchy throats.