Definitions for "Fine particles"
Particles smaller that about 2 mm diameter, which arise mainly from condensation of hot vapours and chemically driven gas-to-particle conversion processes. Often refers to the PM2.5 fraction
Particles with the diameter smaller than 2.5 μ m.
EPA classification of particles having aerodynamic diameters greater than 0.1 micrometer and less than or equal to 2.5 micrometers.