ADDED: Although I was looking for info on the App. I see that the info in the Map Section here carries over to the Map. Still not sure what the discrepancy is with the readings.
ORIGINAL POST: I don’t have a PurpleAir sensor yet, but a number of people have told us about it. So, I just installed the App and have been using the Map to take a look. So far I haven’t found any info on a couple of pretty basic questions. Maybe someone here can give me the answer.
What’s the most common settings people use for the App. The defaults seem to show me much lower numbers than other Air Quality sites. The EPA, State and other sites are showing 125 in the same area the PurpleAir App and Website are showing me 78. So which one is right?
The “Apply conversion” was defaulted to LRAPA, but if I change it to No, the numbers are closer to the other sites. So should it be set to No?
What do Black numbers/characters mean vs Gray ones. Not the color of the dots, but the numerals themselves. There does not seem to be ANY documentation other than the colors of the dots. Is there a REAL manual somewhere that you can search. (PDF or Website)
Everyone seems to rave about the PurpleAir sensors. But so far I’m not convinced with the company and the apparent execution of the App and Website to monitor the data.
Thank you for the questions, I’m going to provide answers below.
The default PurpleAir map settings can be found here: Map Troubleshooting Guide. You’ve said that the map defaulted to using the LRAPA conversion. I’m not sure why that would have happened, but if you want to match default map settings, conversions should be set to “No.”
See above. I also want to mention here that there are a lot of factors that can influence differences in readings. Generally, these have to do with how data is averaged and if conversions are used. For example, the EPA averages our data differently than we do, and if you’re talking about PurpleAir sensors on the Fire and Smoke map, the “EPA Conversion” is used. More information is available here: How do I match PurpleAir's Map with AirNow's Fire and Smoke Map?
We have both a Map Guide and a Map Troubleshooting Guide. The answer you’re looking for might be in one of those guides. I’m not exactly sure what you’re talking about, although it sounds like it could be the differences between high confidence and low confidence sensors. Information regarding that can be found in the map guide.
Thanks for the info Kieran. You may have missed that I did find most of the info.
For #3, I found the answer on another site, again, kind of surprised it wasn’t here. The change from black to white (looked more gray on our phones) is quite simple a Graphics choice. As the color of the dot gets darker, at some point the numbers will change from black to white just to be read easier. Makes total sense, but we had a mix of both and it didn’t see that apparent at the time.