Larger particulate matter suspended in the air settles to the surface of the Earth in a shorter period of time due to its gravity, while a small amount of particulate matter that can be suspended in the air for a long time. Therefore, the environmental protection department usually includes particulate matter with a diameter of less than 100 microns in the air, and is called total suspended particulate matter, which is usually expressed by TSP. TSP is the first letter of the English abbreviation for Total Suspended Particulate, i.e. TSP refers to total suspended particulates in the air 100 microns or less in diameter.
PM10 refers to particles in the air whose diameter is less than or equal to 10 microns (about 1/5 of the thickness of a human hair). Because this part of the particles can enter the nasal cavity and mouth of the human body, it is also called inhalable particles, usually Expressed by PM10. PM is the acronym for English Particulate Matter, and 10 refers to the particle diameter less than or equal to 10 microns.
PM2.5 refers to particles in the atmosphere whose diameter is less than or equal to 2.5 microns (less than 1/20 of the thickness of human hair). It can be seen that PM2.5 is part of PM10. In PM10, this part is called As fine particles, particles with a diameter between 2.5 and 10 microns are called coarse particles, as opposed to fine particles. PM2.5 passes through the respiratory tract and reaches the lungs of the person, directly into the alveoli.
It is not difficult to understand that PM1.0 refers to particles in the air whose diameter is less than or equal to 1.0 micron, also called ultrafine particles.