Imagine that you drive north from Montrose, Colorado to Grand Junction. Air quality starts out pretty good, gets worse. You take I-70 east to Glenwood Springs, then angle southeast, but higher, to Aspen. It looks like the smoke and ash of regional fires (Lee and Elk) flow up both Colorado and Roaring Fork rivers. Upvalley. I felt it in my lungs which is what got me interested. Here's the key to my slapped together chart. 0 to 50 = Good 51 to 100 = Moderate 101 to 150 = Unhealthy for sensitive groups 151 to 200 = Unhealthy 201 to 300 = Very unhealthy 301+ = Hazardous I suspect this random bit of citizen science (data points from public resources) is no more than that. But wildfires move fast and fire isn't the only concern.