Assuming you care PM1.0/PM2.5 (which are what are truly harmful), and want R^2 >0.9: Atmotube pro Elitech (for PM2.5) Purpleair The field evaluations have goo

Assuming you care PM1.0/PM2.5 (which are what are truly harmful), and want R^2 >0.9: Atmotube pro Elitech (for PM2.5) Purpleair The field evaluations have good expositions of the underlying data in slide form. For sure the purpleair is the best bet that i can see. Note that they are pragmatic as well - if you read field evaluations, AQMD folks generally think >0.8 R^2 is very good. Which probably makes sense comparing a $50-$250 device to a several thousand dollar reference instrument. Note that one serious issue is that a bunch of the sensors aren't just uncorrelated, they are often dramatically undercounting. It would be one thing if they were dramatically overcounting, and told you air was horrible when it wasn't. But they are actually telling you air is fine when it isn't even close to fine. I actually went down the same path as OP about 6 months ago. I have used a dylos meter in my old woodshop, and was building a new one, and wanted to see what the the best thing to do was. After a bunch of looking, i found these folks. I am not aware of others doing this breadth of testing. (It turn out the dylos meter is either accurate, or overcounts, depending on temperature/humidity. This is actually acceptable since it won't tell me things are good when they are bad, but it also turned out the purpleair was consistently good for the same price :P)