State Air PM2.5 data

State Air makes their data available under specific conditions and with limitations. Here is a listing from their website giving them:

There are some differences in the data between their site and mine. They have a good number of readings with negative concentration values, which cannot be correct. I have deleted those readings, rather than replace them with 0. There could also be import errors where my data differs from theirs, though I think I have caught most of those.