Definitions for "Respirable particles"
particles smaller than about 2.5 microns in diameter, which arise mainly from condensation of hot vapours and chemically-driven gas to particle conversion processes; also referred to as PM2.5. These are fine enough to penetrate deeply into the lungs and have the greatest effects on health.
Airborne particles within a size range that allows them to be inhaled and to penetrate deeply into the lungs.
Particles which can penetrate to the alveolar regions of the lung