How is air quality measured?

As smoky air from Canada’s wildfires shrouds broad swaths of the U.S., here are seven facts you should know about measuring air quality.

Air Quality Alert in effect in Southeast Michigan -- What the AQI colors mean

In the Detroit area, the Environmental Protection Agency's Air Quality Index (AQI) has been between Orange (unhealthy for sensitive groups) and Purple (very unhealthy) with some areas occasionally moving into the Maroon (hazardous) level on Wednesday. Here's what that means for your health: