When an air quality alert is issued, the single most important step is to reduce the time you spend outdoors and keep your indoor air as clean as possible. Most alerts are triggered by wildfire smoke, ground-level ozone, or industrial pollution pushing the Air Quality Index (AQI) above 100. What you need to do depends on how high the AQI climbs and whether you fall into a sensitive group.
Understanding AQI Levels
The AQI runs from 0 to 500, divided into six color-coded tiers. At green (0 to 50), air is clean and safe for everyone. Yellow (51 to 100) is acceptable for most people, though unusually sensitive individuals may notice mild effects. Orange (101 to 150) is where formal air quality alerts typically begin, signaling risk for sensitive groups. Red (151 to 200) means even healthy adults can experience symptoms. Purple (201 to 300) is a health alert for everyone, and maroon (301 and above) is an emergency.
You can check real-time AQI readings at AirNow.gov or through weather apps on your phone. The number can shift significantly over the course of a day, especially during wildfire events, so check more than once.
Who Is Most at Risk
Sensitive groups include children, adults over 65, people with asthma, chronic bronchitis, emphysema, or heart disease, and anyone who works or exercises outdoors for extended periods. If you fall into any of these categories, start taking precautions at the orange level (AQI 101). Everyone else should act once the AQI crosses into red (151) or higher.
Limit Outdoor Activity by AQI Level
At AQI 101 to 150, healthy adults can still be active outside, but pay attention to warning signs: watery eyes, sore throat, headache, coughing, or unusual shortness of breath. If any of those appear, move indoors. Sensitive groups should cut back on prolonged or strenuous outdoor exercise.
At AQI 151 to 200, everyone should limit strenuous outdoor activity lasting more than one hour. At 201 to 300, avoid strenuous outdoor activity altogether. Above 300, stay indoors as much as possible and skip any unnecessary trips outside.
If you normally run, bike, or do yard work, move your workout inside on alert days. Breathing harder during exercise pulls more polluted air deeper into your lungs, amplifying the harm.
Keep Your Indoor Air Clean
Staying inside only helps if your indoor air is actually better than what’s outside. Start by closing all windows and exterior doors. If you have a central HVAC system, set it to recirculate rather than drawing in fresh air, and run the fan continuously to keep pushing air through the filter.
Most home HVAC systems come with a basic MERV-8 filter. Upgrading to a MERV-13 filter makes a meaningful difference because it traps much smaller particles, including the fine particulate matter (PM2.5) that’s responsible for most smoke-related health effects. These particles are small enough to penetrate deep into your lungs and even enter your bloodstream, causing respiratory and cardiovascular symptoms. Before upgrading, confirm that your system can handle the higher-rated filter; some older units struggle with the increased airflow resistance.
A portable air purifier with a HEPA filter is the next best option, especially if you don’t have central air. To size one correctly, calculate the volume of your room (length × width × height in feet) and multiply by at least 4.8. That gives you the minimum Clean Air Delivery Rate (CADR) you need. Ignore the room-size claims on the box and run your own numbers. If you can, get a unit with a higher CADR than you need so you can run it on a lower, quieter fan speed.
If you have neither a good HVAC filter nor a purifier, you can build a basic one by taping a MERV-13 furnace filter to the back of a box fan. It’s not as effective as a commercial purifier, but it will noticeably reduce particle levels in a single room.
Protect Yourself When You Must Go Outside
An N95 respirator is the best widely available option for filtering fine particles. Surgical masks and cloth masks do very little against PM2.5. Even an N95, though, only works well when it seals tightly against your face. In real-world conditions, with imperfect fit, breaks for eating or drinking, and the simple fact that most people don’t wear them every minute, researchers estimate roughly a 50% reduction in particle exposure over a full day. That’s still a significant improvement.
To get the best seal, press the metal nosepiece firmly against the bridge of your nose, pull the straps snug behind your head (not your ears, on most N95 models), and check for air leaking around the edges. If you feel air flowing past your cheeks or nose when you inhale, readjust. People with facial hair will have a harder time getting a proper seal.
Driving During an Alert
Your car cabin can fill with polluted air quickly if you’re pulling in outside air. Switch to recirculation mode on your climate controls, which recycles the air already inside the cabin through the cabin filter multiple times. Research shows that full recirculation drops particle counts dramatically, but it also causes carbon dioxide to build up inside the car, which can make you drowsy.
The practical solution is partial recirculation. Running the system at about 50% to 75% recirculation keeps particle levels well below outdoor concentrations while allowing enough fresh air to keep CO2 at comfortable levels. Some vehicles have only a full recirculate toggle. In that case, cycle recirculation on for 15 to 20 minutes, then briefly switch to fresh air for a few minutes before switching back. Keep windows fully closed either way.
Avoid Adding to Indoor Pollution
On alert days, skip anything that generates particles inside your home. That means no candles, incense, gas stoves used without ventilation, or wood-burning fireplaces. Frying and broiling food also release fine particles, so stick to lower-smoke cooking methods or use a range hood that vents outside. Vacuuming with a standard vacuum can stir up settled particles; use one with a HEPA filter or hold off until after the alert clears.
Recognize Symptoms That Need Attention
Fine particle pollution irritates your airways and stresses your cardiovascular system. Common symptoms include coughing, scratchy throat, stinging eyes, mild headache, and shortness of breath. These typically ease once you get into clean air. More concerning signs are chest tightness, heart palpitations, persistent difficulty breathing, or worsening asthma that doesn’t respond to a rescue inhaler. Those warrant medical attention promptly.
People with existing heart or lung conditions are at higher risk for serious events during poor air quality episodes, including heart attacks and severe asthma attacks. If you have a chronic condition, keep medications readily accessible and follow any action plan you’ve discussed with your provider.
Cleaning Up After the Alert Ends
Once the AQI drops back to green or yellow, don’t just throw open the windows immediately. If smoke or ash settled during the event, you’ll want to clean surfaces first to avoid stirring particles back into the air you breathe.
Indoors, wipe hard surfaces with a damp cloth and wet-mop floors. Do not dry sweep, and only vacuum if your machine has a HEPA filter. A regular vacuum will blow fine particles right back into the room. If you have a portable air purifier, keep it running while you clean.
Outdoors, gently dampen any visible ash before touching it. Avoid pressure washers, which blast ash into the air before wetting it, and never use a leaf blower or shop vacuum on ash. A HEPA-equipped vacuum works best. If you don’t have one, gently scoop or sweep dampened ash into bags for disposal. Once surfaces are clean, you can open windows to ventilate your home with the now-cleaner outdoor air.