Stations with readings of 0


I’m relatively new here. Our team uses purple air APIs to fetch AQ data in the Mongolian region. We see some readings on the real time map that display 0 and after checking out individual sensor readings in the stations, they individually show vastly different readings, which I suspect then get aggregated to 0 because they can’t agree on a value.

My questions are:

  1. What method do PA use to calibrate, aggregate different sensor readings into a singular station value?
  2. Is there a way for us to directly fetch individual sensor readings?

Hi @Bat

I’ll quickly say that the most common reason a sensor reads zero is that one of the channels has a broken fan.

  1. On the PurpleAir map, readings for both of a sensor’s channels are averaged to produce the singular value. This is the same in the API, if you pull “pm2.5_cf_1,” for example, that field is averaging the pm2.5 data from both of that sensor’s channels.

  2. You can retrieve data from individual channels in a sensor. Using the same example as above, instead of querying “pm2.5_cf_1,” you could pull both “pm2.5_cf_1_a” and “pm2.5_cf_1_b.” When you see “a” and “b” in the API documentation, that is going to be the two individual channels in a device.