Air Quality Index Health Ratings
Values from 'Wildfire Smoke – A Guide for Public Health Officials', Updated June 2013

US EPA has developed an Air Quality Index (AQI) (see chart below) to provide easy to understand information on local air quality and whether air pollution levels pose a health concern.

Air Quality Index health rankings are based on 1-hour and 24-hour concentration averages. EPA developed the health indices based on 24-hour averages. Idaho State’s Department of Environmental Quality developed health indices based on 1-hour averages.

AQI Category
(AQI Values)
PM2.5 or PM10 Levels (ug/m3) Visibility - Arid Conditions (miles) Recommended Actions
1-3 hr avg 8 hr avg 24 hr avg
Good
(0-50)
0 –38 0 – 22 0 – 12 >= 11
  • If smoke event forecast, implement communication plan
Moderate
(51 – 100)
39 – 88 23 – 50 12.1 – 35.4 6 – 10
  • Issue public service announcements (PSAs) advising public about health effects and symptoms and ways to reduce exposure
  • Distribute information about exposure avoidance
Unhealthy for Sensitive Groups
(101 - 150)
89 – 351 51 – 79 35.5 – 55.4 3 – 5
  • If smoke event projected to be prolonged, evaluate and notify possible sites for cleaner air shelters
  • If smoke event projected to be prolonged, prepare evacuation plans
Unhealthy
(151 – 200)
139 – 351 80 – 200 55.5 – 150.4 1.5 – 2.75
  • Consider “Smoke Day” for schools (i.e., no school that day), possibly based on school environment and travel considerations
  • Consider canceling public events, based on public health and travel considerations
Very Unhealthy
(201 – 300)
352 – 526 201 – 300 150.5 – 250.4 1 – 1.25
  • Consider closing some or all schools (Newer schools with a central air cleaning filter may be more protective than older, leakier homes. See “Closures”, below.)
  • Cancel outdoor events (e.g., concerts and competitive sports)
Hazardous
(>300)
> 526 > 300 250.5 - 500 < 1
  • Close schools
  • Cancel outdoor events (e.g., concerts and competitive sports)
  • Consider closing workplaces not essential to public health
  • If PM level is projected to remain high for a prolonged time, consider evacuation of sensitive populations