Wildfire Smoke and Air Quality: How to Read the AQI and Protect Your Health
How wildfire smoke affects your health, what the Air Quality Index (AQI) colors mean, who is most at risk, and practical steps to protect yourself and your family, including N95 masks, air purifiers, DIY box fan filters and a clean-air room.
The sky turns a strange orange-gray. The sun looks like a red coin. You can smell smoke inside your house even though the nearest fire is hundreds of miles away. Your eyes sting, your throat feels scratchy and your phone keeps sending air quality alerts you're not quite sure how to read.
Wildfire smoke used to be something most people only worried about if they lived near a fire. That's changed. Larger, longer fire seasons in North America have sent smoke drifting across states and even countries, and in 2023 smoke from Canadian wildfires pushed air quality in New York City and other eastern cities to some of the worst levels in the world for a time. Knowing how to read air quality and protect yourself is now a basic life skill.
Why wildfire smoke is harmful
Wildfire smoke is a mix of gases and fine particles from burning trees, plants, buildings and other materials. The biggest health concern is fine particulate matter, known as PM2.5. These particles are 2.5 micrometers or smaller, about 30 times thinner than a human hair. They're small enough to travel deep into your lungs and even enter your bloodstream.
Short-term exposure to smoke can cause:
- Burning eyes and a runny nose
- Scratchy throat and coughing
- Headaches
- Wheezing and shortness of breath
- Chest pain or a fast heartbeat
- Fatigue
- Worsening asthma, COPD or heart conditions
Research has linked wildfire smoke exposure with more emergency room visits for breathing problems, and long-term exposure to fine particle pollution in general is associated with heart and lung disease.
Who is most at risk from wildfire smoke?
Anyone can be affected by smoke, but some people face higher risk:
- Children, because their lungs are still developing and they breathe more air relative to their body size
- Older adults
- Pregnant people
- People with asthma, COPD or other lung diseases
- People with heart disease or diabetes
- Outdoor workers
- People without stable housing, who may have no indoor place to escape smoke
How to read the Air Quality Index (AQI)
The Air Quality Index, or AQI, is a color-coded scale used in the U.S. to show how clean or polluted the air is. The higher the number, the worse the air.
| AQI | Color | What it means |
|---|---|---|
| 0 to 50 | Green | Good. Air quality is satisfactory. |
| 51 to 100 | Yellow | Moderate. Unusually sensitive people may want to limit long or heavy outdoor exertion. |
| 101 to 150 | Orange | Unhealthy for sensitive groups. People at higher risk should reduce outdoor activity. |
| 151 to 200 | Red | Unhealthy. Everyone may begin to feel effects; sensitive groups may feel more serious ones. |
| 201 to 300 | Purple | Very unhealthy. Health alert for everyone. |
| 301 and higher | Maroon | Hazardous. Emergency conditions. |
You can check current local air quality at AirNow.gov, the EPA's site, or in many weather apps. During smoke events, the PM2.5 reading is usually the one that matters most.
Keep in mind that smoke levels can change quickly, so check throughout the day.
How to protect yourself from wildfire smoke
Stay indoors and keep smoke out
When air quality is unhealthy, the best thing you can do is stay inside with windows and doors closed. If you have central air, set it to recirculate so it isn't pulling in outdoor air.
Create a clean-air room
Pick one room in your home, ideally a bedroom, and make it as clean as possible:
- Keep windows and doors closed
- Run a portable HEPA air purifier sized for the room
- Avoid activities that add particles, like frying food, burning candles, smoking or vacuuming with a non-HEPA vacuum
- Keep the room cool, especially during heat waves. See our extreme heat safety guide, since smoke and heat often arrive together.
Use air purifiers and better filters
- Portable HEPA air purifiers can significantly reduce indoor smoke particles. Choose one sized for your room based on its CADR rating. Our guide to whether air purifiers and houseplants work explains how to choose.
- HVAC filters: If you have central heating and cooling, a MERV-13 or higher filter can help, if your system can handle it.
- DIY box fan filter: A Corsi-Rosenthal box made from a box fan and MERV-13 furnace filters is an affordable, effective option tested by researchers. Even a single MERV-13 filter taped to the back of a box fan helps. Use newer box fans with safety features, and don't leave them unattended.
Wear an N95 mask outside
If you must go outside on smoky days, wear a well-fitted N95 or KN95 respirator. Cloth masks, surgical masks and bandanas won't protect you from fine smoke particles. Make sure the mask seals well around your nose and mouth. N95 masks aren't designed for young children and may not fit them properly.
Limit outdoor exercise
When air quality is unhealthy, skip hard outdoor workouts. You breathe more deeply and quickly during exercise, pulling more smoke into your lungs. Move your workout indoors, or switch to gentle activity at home.
Be careful in the car
Keep windows closed and set the air to recirculate when driving through smoky areas.
Avoid adding more pollution
On smoky days, skip burning candles, incense or wood fires, and avoid using gas stoves without ventilation.
Prepare before fire season
If you live in or near fire-prone areas, or anywhere that's had smoke events before, plan ahead:
- Buy an air purifier and spare filters
- Stock N95 masks for every adult in your household
- Keep a supply of medications, especially inhalers
- If you have asthma or heart disease, talk to your doctor about an action plan
- Know where your community's clean-air shelters or cooling centers are
- Sign up for local emergency alerts
- If you live near fires, have an evacuation plan and a go-bag ready
Protecting children and pets
- Keep kids indoors on unhealthy air days and plan indoor activities
- Watch for coughing, wheezing or trouble breathing
- Schools and sports programs may cancel outdoor activities, which is a good thing
- Bring pets inside too. Animals can be harmed by smoke, and dogs especially may need shorter walks.
When to get medical help
Seek medical care if you or someone in your household has:
- Trouble breathing or shortness of breath that doesn't improve
- Chest pain or tightness
- A racing or irregular heartbeat
- Severe coughing or wheezing
- Dizziness or confusion
Call 911 for a medical emergency.
Wildfire smoke and mental health
Smoke events can be stressful too. Being stuck indoors, worrying about loved ones near fires or watching orange skies can stir up anxiety. If it's weighing on you, our guide to climate anxiety has coping strategies. Staying connected with friends, keeping some routine and moving your body indoors all help.
After the smoke clears
Once air quality improves, a few steps help you reset your home:
- Air out your home. Check that the AQI is in the green or yellow range, then open windows to bring in fresh air.
- Change filters. HVAC filters and air purifier filters can fill up fast during smoke events. Check them and replace as needed.
- Clean surfaces. Wipe down surfaces with a damp cloth and vacuum with a HEPA vacuum to remove settled ash and particles.
- Be careful with ash. If you live near a burned area, avoid stirring up ash, wear an N95 mask and gloves when cleaning, and don't let children play in ash.
- Watch your health. If you notice lingering cough, wheezing or fatigue, talk to your doctor.
Smoke and outdoor workers
If your job keeps you outdoors, smoke days are especially tough. Some states have rules requiring employers to provide N95 respirators and take other steps when air quality reaches certain levels. Ask your employer about their wildfire smoke plan, take breaks indoors in filtered air when possible and speak up if you have symptoms.
Frequently asked questions
What AQI level is unsafe?
An AQI above 100 is unhealthy for sensitive groups, such as children, older adults and people with heart or lung disease. Above 150 is considered unhealthy for everyone.
Do masks protect against wildfire smoke?
Well-fitted N95 or KN95 respirators can protect against fine smoke particles. Cloth and surgical masks don't provide much protection.
Does an air purifier help with wildfire smoke?
Yes. Portable air purifiers with HEPA filters can significantly reduce indoor smoke particle levels, especially in a closed room.
Should I open windows after wildfire smoke?
Wait until outdoor air quality improves, then open windows to air out your home. Check the AQI before opening up.
How long does wildfire smoke stay in the air?
It depends on the fire and the weather. Smoke can linger for hours, days or even weeks, and conditions can change quickly as winds shift.
Clean air is the foundation of environmental wellness. Find out how your environment is supporting you with our free wellness wheel quiz.
