Each Air Quality Index category, also known as the level of concern, is attached to a certain range of values: Good (green): 0 to 50; Moderate (yellow): 51 to 100; ...

As smoke from Canadian wildfires has made its way into the U.S., it is important to understand how the air quality index works. Here's what each color code means.

The Air Quality Index does not take into account many gas or particle contaminants that are produced during wildfires, particularly when houses, cars and other man-made materials go up in flames.

The Air Quality Index tracks this kind of pollution with a measurement known as PM 2.5, which quantifies the concentration of particles smaller than 2.5 micrometers in the air.

Here’s how to understand the Environmental Protection Agency’s Air quality index (AQI), which measures, on a 300-point scale (along with six categories and advisories), the quality of air in ...

The Southwest Ohio Air Quality Agency reports that "levels of ozone within the region may approach or exceed unhealthy ...