A: PurpleAir PA-II and PA-II-SD sensors contain two laser particle counters that measure the real time particulate matter and report as Channel A and Channel B. If the values being reported for the two laser particle counters drift apart, our system may “downgrade” one of the channels. The downgraded channel will no longer be used in the data average and will be grayed out in the graph’s legend. You can still view the downgraded channel on the graph by clicking on the downgraded name in the graph’s legend.
If you feel like the wrong channel has been downgraded, please contact us.
Learn more about channels reporting high, not working, or spikes erratically.
Learn more about sensor maintenance.