AQI charts — which look at the amount of PM2.5 and other pollutants like ozone in the air — are typically displayed in different tiers: 0 to 50 – The air is good.

As the chart shows, for PM2.5 concentrations up to 60 microgram per cubic metre (µg/m3), AQI increases by 1.67 for every 1µg/m3 increase in PM2.5 concentration.

The EPA's Air Quality Index can tell you whether breathing outside air can hurt you. ... On the AQI, particulate matter readings, labeled "PM2.5," range from 0-301 or higher, and ...

As the chart shows, for PM2.5 concentrations up to 60 microgram per cubic metre (µg/m3), AQI increases by 1.67 for every 1µg/m3 increase in PM2.5 concentration.