Pennsylvania is under a statewide Code Purple air quality alert on Friday because of smoke from the wildfires in Canada and Minnesota. But what does that mean?

Air quality alerts can change quickly during wildfire smoke events. Here’s what Code Orange and Code Red mean, who is most at risk and when you should limit time outside.

What are "Code Red" and "Code Purple" air quality alerts? The Air Quality Index has six color-coded categories, ranging from cleanest to hazardous.

Wildfire smoke from Canada and Minnesota will cause unhealthy air across the state. Residents are urged to limit outdoor activity and check local air quality conditions. PHILADELPHIA - The ...