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 Air Quality Index on the Oregon Department of Environmental Quality website spent at least a portion of Monday and Tuesday, Aug. 24-25, above 100, placing it in a range the DEQ says is ...