The sum of all particles smaller than 10 in diameter is referred to as PM10 . As such PM10 includes the contribution of PM2.5.
PM1 is the sum of all particles smaller than 1 in diameter. Such particles are also referred to as submicron particles. Conversely super micron particles and those larger then 1 in diameter. Hydrometeor particles generally range from 5 to 8 mm in diameter although hail can reach 115 mm in diameter.