°any microscopicparticle less than about 100 nanometers (nm) in diameter. In aerosol science, the term is often reserved for particles less than 50 nm in diameter; the term "ultrafine particles" is used for particles less than 100 nm in diameter.
°any microscopicparticle less than about 100 nanometers (nm) in diameter. In aerosol science, the term is often reserved for particles less than 50 nm in diameter; the term "ultrafine particles" is used for particles less than 100 nm in diameter.