AQI (air quality index)

An air quality index (AQI) is a number used by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become. As the AQI increases, an increasingly large percentage of the population is likely to experience increasingly severe adverse health effects. Computation of the AQI requires an air pollutant concentration over a specified averaging period, obtained from an air monitor or model. Taken together, concentration and time represent the dose of the air pollutant.

stay indoors

wear a mask outdoors

use an air purifier

seek higher altitudes

• Masks can be bought from hardware stores or online. The most effective masks are those with the words "particulate respirator", "NIOSH", and either "N95" or "P100" in its title.
• Air purifiers can be bought from Home Depot, Costco, or online.
• AirNow has updated information on the air quality in all regions.