Most particles by total mass, but not by total health risk. Your phone LED test only detects large particles that your lungs can remove (see https://en.wikipedi

Most particles by total mass, but not by total health risk. Your phone LED test only detects large particles that your lungs can remove (see https://en.wikipedia.org/wiki/Mucociliary_clearance https://en.wikipedia.org/wiki/Mucociliary_clearance ). PM2.5 particles are more dangerous because they can make it past the lungs' self-cleaning system, and the very smallest ones can penetrate the lungs and end up in the bloodstream. You need a laser sensor to measure small particles.