Frequently Asked Questions

How is the WAQR different from the Air Quality Index?

Federal Air Quality Index vs. State’s Wildfire Air Quality Health Rating

The Air Quality Index (AQI) is a federal index that is standardized across the country. The AQI health level is based on 24 hour averages for PM_2.5 and its long averaging time smoothes out real time forest fire smoke plume impacts. The WAQR was develop in response to the Natural Events Action Plan for Wildfires to measure forest smoke plumes and report health impacts based on an hourly basis. The WAQR is only used in Oregon and is similar to ratings used in Montana and Idaho.

Averaging Time

AQI health levels are based on 24 hour averages for PM_2.5, 8 hour average for Ozone and Carbon Monoxide. These average times do not address effects of forest fire smoke plumes which can change PM_2.5 levels quickly. The WAQR ratings are based only on PM_2.5 and include the highest value of the 1 hour, 8 hour, or 24 hour average. The 1 hour average time will measure immediate impacts from forest fire smoke plumes

Calculation differences

Continuous PM_2.5 concentrations are calculated using a correlation equation based on collocated PM_2.5 filter data and nephelometry visibility data. The correlation equations are different for forest fire smoke impacts and other more local impacts such as wood stove smoke. The AQI uses a daily average over a year's time period to estimate PM_2.5 for typical PM_2.5 health levels. The WAQR uses the forest fire events only to develop a correlation.

Why do we need a WAQR?

During recent forest fires the AQI showed a health level of "Good" while Medford and Klamath Falls were inundated with forest fire smoke. The AQI didn't report "Unhealthy" because it was developed for traditional impacts which take many hours to form and don't dissipate quickly. Forest fire plumes can inundate a community quickly and move when the wind changes. The WAQR's 1 hour averaging time should account for these more immediate impacts and will supersede the AQI during forest fire smoke impacts.

Why are there two estimates for PM2.5? Which one is correct?

The AQI calculates PM_2.5 continuously and is accurate during non forest fire conditions. During forest fire impacts the AQI over predicts health levels over many hours and under reports health levels for short term impacts. During forest fires the WAQR supersedes the AQI. To determine what areas are being impacted go to the National Interagency Fire Center.

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