What I want to do or know
There are a lot of really neat optical monitors coming out around particulate matter sensing. Specifically I've heard about people using the Spec and the Air Beam. There's a new one (to me) that @MD2020 and @guolivar recently referenced on the air-quality google group called "Purple Air." It seems really interesting, but I am wondering about what environmental factors these sensors take into account in producing their readings. Particularly, I've heard humidity can affect the results of these optical monitors. Looking into the Purple Air page, it looks like only some of the Purple Air monitors have humidity sensing add-ons, and it's unclear if or how this data relates to the results. Looking for more information about this question if anyone has ideas or resources!