Wash. Admin. Code § 296-820-860
The Air Quality Index (AQI) for PM2.5 is calculated as follows:
PM2.5 THRESHOLDS1 | AQI1 | AQI CATEGORY1 | WA DOH HEALTH MESSAGING2 |
0.0-12.0 | 0-50 | Good | It is a great day to be active outside and a good time to make a plan if worse air quality is in the forecast. |
12.1-35.4 | 51-100 | Moderate | Some people are especially sensitive to lower levels of particle pollution and should reduce exposure. For example, limit time outside and avoid strenuous outdoor activity. All sensitive groups should watch for symptoms. |
35.5-55.4 | 101-150 | Unhealthy for sensitive groups | Sensitive groups should take steps to reduce exposure. Limit time outside, avoid strenuous outdoor activity, and follow tips for cleaner indoor air. Everyone should watch for symptoms as a sign to reduce exposure. |
55.5-150.4 | 151-200 | Unhealthy | Everyone should reduce exposure. Limit time outside, avoid strenuous outdoor activity, and follow tips for cleaner indoor air. |
150.5-250.4 | 201-300 | Very unhealthy | Everyone should reduce exposure. Stay inside and filter indoor air to keep it cleaner. Go elsewhere for cleaner air, if needed. |
250.5-350.4 | 301-400 | Hazardous | Everyone should reduce exposure. Stay inside and filter indoor air to keep it cleaner. Go elsewhere for cleaner air, if needed. |
350.5-500.4 | 401-500 | Hazardous | Everyone should reduce exposure. Stay inside and filter indoor air to keep it cleaner. Go elsewhere for cleaner air, if needed. |
[GREATER THAN] 500.4 | Beyond the AQI | Hazardous (beyond the AQI) |
1 U.S. EPA. September 2018. Technical Assistance Document for the Reporting of Daily Air Quality - The Air Quality Index (AQI). EPA 454/B-18-007. Research Triangle Park, North Carolina.
2 Washington Department of Health. April 2022, accessed April 2023. Washington Air Quality Guide for Particle Pollution: https://doh.wa.gov/sites/default/files/legacy/Documents/4300/waqa%20infographic%5fEnglish.pdf?uid=64384c71c8715
Wash. Admin. Code § 296-820-860