The AQI scale, decoded
The EPA's Air Quality Index runs from 0 to 500 across six color bands. Green (0-50) is good and yellow (51-100) is moderate. Orange (101-150) is unhealthy for sensitive groups: children, older adults, and anyone with heart or lung conditions. Red (151-200) is unhealthy for everyone. Purple (201-300) is very unhealthy, and maroon (301+) is hazardous, emergency-level air.
During major fire events, downwind cities can hit purple and maroon readings hundreds of miles from the flames. The AQI layer on our map uses this exact EPA scale.
Why smoke is more than a nuisance
The main threat in wildfire smoke is PM2.5: particles smaller than 2.5 micrometers, about 30 times thinner than a human hair. They bypass your nose and throat, lodge deep in the lungs, and can enter the bloodstream. Short-term exposure triggers asthma attacks, chest pain, and heart events; children, pregnant people, older adults, and outdoor workers face the highest risk.
Symptoms like burning eyes, scratchy throat, coughing, and headaches are your body's early warning. If air smells smoky or visibility is noticeably reduced, PM2.5 is elevated even before official monitors update.
What actually protects you
Indoors: close windows and doors, run an air purifier with a HEPA filter or set your HVAC to recirculate with the best filter it accepts (MERV 13 if possible), and avoid adding indoor pollution from candles, frying, or vacuuming. A single room with filtered air beats lightly filtering a whole house.
Outdoors: an N95 or KN95 respirator that seals to your face filters most PM2.5. Cloth masks and surgical masks do very little against smoke. Cut outdoor exercise when the AQI is orange or worse for you, and check AirNow.gov's Fire and Smoke Map for monitor readings near you.
Frequently asked questions
As long as PM2.5 stays elevated, which depends on fire activity and wind. Air can flip from hazardous to good in hours when the wind shifts, so check readings rather than assuming.
Maps interpolate between monitors, so local readings can differ, especially in terrain. Treat map colors as a strong guide and your senses (smell, visibility) as a real-time check.
Official sources
This guide summarizes the following government publications. Read them for full detail.
Keep learning
Ready to put it to use? Check the live wildfire map or get an instant risk report for your address with the search on the homepage.