On: Ask HN: What equipment measures mold, dust, tree, grass and ragweed levels?

[BostonEnginerd]

You can measure gross particulate levels with indication of sizing using something like this:

https://www.sparkfun.com/products/9689

This would give you some indication of what's floating around. Further analysis like what dalke mentioned would be necessary to figure out exactly what the particulate makeup is.

edit - The sharp sensor does not give an indication of sizing.