Palo Alto Air Quality Information

Weather—Air Quality—Seismic Activity

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PaloAltoWeather.com Uses the US EPA Correction

The United States Environmental Protection Agency (US EPA) has developed a correction for Purple Air sensors that performs better than either Purple Air's uncorrected PM2.5 concentrations (which report high in wood fire situations) and LRAPA corrected concentrations (which report low when AQI exceeds 150).

PurpleAir devices with the US EPA correction report the correct AQI category 92% of the time and within one category 100% of the time. This performance holds true even for smoke only events.

As of October 4, 2020 at 2:00 PM PDT, PaloAltoWeather.com reports PM2.5 and PM2.5 AQI with the US EPA correction. The uncorrected and LRAPA values are no longer reported.

All historical graphs have been updated to reflect the US EPA correction.

For information on what you can do to proect yourself, see Berkeley Lab's How to Protect Yourself From Wildfire Smoke.

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