Even outdoors, humidity is a problem. Humidity turns little particles into bigger, soggier particles that give higher readings on optical sensors, which can rat

Even outdoors, humidity is a problem. Humidity turns little particles into bigger, soggier particles that give higher readings on optical sensors, which can rather inflate readings on cheap sensors in humid or foggy conditions. There’s a reason that the actual EPA particle counting standards involve drying the particles before measurement. (RIP, EPA.)