If you have used PurpleAir in the past and compared it to the official AQI on , you may have noticed some discrepancies.
The first is that some PurpleAir monitors are placed indoors. You can click off this feature to only display PurpleAir monitors outside, or vice versa - see the diagram below.
The other factor is the type of air pollution, particularly for the Bay Area. We get a lot of wildfire smoke and this can cause inaccuracy in the PurpleAir monitors skewing the results high. The PurpleAir Map website comes with an easy conversion factor you can apply when the majority of the air pollution is from wildfire smoke. You can choose the options of LARPA, AQandU, WOODSMOKE, or US EPA to see a truer representation of the air quality during wildfire smoke events - see the diagram below. The PurpleAir goes into detail about the conversion factors, and each can be explored in detail.
