How Long Is It Safe to Be Outside by AQI Level?
As air pollution rises, it puts more strain on your lungs and cardiovascular system, so adjusting how long you stay outside matters. This calculator uses the US EPA's Air Quality Index (AQI) categories — Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous — to give a rough recommended maximum outdoor activity time. Enter today's AQI number (from your weather app or AirNow.gov) to see your category and activity guidance instantly.
Why the Time Limit Changes by Category
Fine particulate matter (PM2.5) is small enough to travel deep into the lungs, so the higher the AQI, the more important it is to limit exposure time. Starting at "Unhealthy for Sensitive Groups," children, older adults, and people with asthma or heart conditions should cut back on prolonged outdoor exertion. Once AQI crosses into "Unhealthy" and beyond, even healthy adults should shorten outdoor time and consider wearing an N95 mask, which is far more effective at filtering fine particles than a cloth mask.
Exercise Intensity Changes Your Real Exposure
A brisk run and a slow walk at the same AQI level don't carry the same risk — heavier breathing during intense exercise pulls in more polluted air overall. On high-AQI days, it's smarter to move workouts indoors or lower the intensity rather than pushing through outside. For unavoidable trips like commuting, shortening your route and avoiding busy roadsides can meaningfully cut your exposure even without changing the AQI itself.
Frequently Asked Questions
Most weather apps and AirNow.gov display a real-time AQI number for your location. Enter that number here to get an activity time recommendation based on EPA air quality categories.
Wear a well-fitted N95 mask, keep outdoor time as short as possible, and avoid any strenuous activity. Wash up and ventilate indoor spaces after returning to reduce further exposure.