AQI Health Advice Calculator
The air quality number is on every weather app, but what to actually do about it isn't. Enter today's reading and your sensitivity profile to get plain-language advice on whether it's safe to go outside. Nothing uploaded.
Result
ModerateWhat to do
Normal outdoor activity - no restrictions.
EPA AQI categories and health guidance
How the EPA defines air quality categories
The EPA's Air Quality Index (AQI) is a 0-500 scale measuring five pollutants: fine particulates (PM2.5 - the most harmful), coarse particles, ozone, nitrogen dioxide, and sulfur dioxide. The reported AQI is the highest of these five pollutants' readings. At AQI 0-50 (Good), all five are at safe levels. At AQI 100 (Moderate), the worst pollutant is at the Moderate level. AQI 150 means at least one pollutant exceeds the "Unhealthy for Sensitive Groups" threshold - typically PM2.5 from wildfire smoke or ozone from summer heat and vehicle emissions. AQI above 300 (Hazardous) warrants staying indoors entirely and running an air purifier.
Sensitive groups vs general public guidance
The EPA provides two activity recommendations: one for the general public and one for sensitive groups (people with asthma, heart/lung disease, pregnant people, older adults, children). At AQI 75-100, general public can do outdoor activity normally, but sensitive groups should reduce vigorous exertion - no running or sports, but light walking is usually safe. At AQI 151-200 (Unhealthy), the guidance reverses: general public should reduce exertion, and sensitive groups should avoid outdoor activity entirely. Always apply the more restrictive guidance if you're unsure which category applies to you.
FAQ
What does AQI actually measure?
AQI (Air Quality Index) is a scale from 0-500 measuring five pollutants: fine particulates (PM2.5), coarse particles (PM10), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2). The EPA reports the highest of these five, so AQI 150 means at least one pollutant is at the 'Unhealthy for Sensitive Groups' level. Wildfire smoke typically drives PM2.5 readings; urban pollution often drives ozone.
Who counts as a 'sensitive group'?
The EPA defines sensitive groups as people with asthma, heart or lung disease, pregnant people, older adults (65+), and children (under 15). These groups experience symptoms at lower AQI readings than the general public. If you fall into any of these groups, follow the sensitive-group guidance. Even if you don't, if a family member does, apply those recommendations to protect them.
Can I exercise outdoors at an AQI of 100-150?
For general public: yes, with normal precautions. For sensitive groups: avoid vigorous exercise outdoors. Vigorous means heavy exertion - running, cycling fast, high-intensity sports. Light activities like walking are usually fine at these levels, but if you have asthma or respiratory disease, take extra precautions or move indoors. If AQI exceeds 151, even general public should reduce outdoor exertion.