Composed of distinct particles. Smoke is particulate; pure gases are not.

Particulate matter may be in the form of fly ash, soot, dust, fog, fumes

Condensable Particulate Matter

Particulate matter, contained almost entirely within the PM2.5 classification, that forms from condensing gases or vapours. It forms by chemical reactions as well as by physical phenomena.

Fine Particles

EPA classification of particles having aerodynamic diameters greater than 0.1 micrometer and less than or equal to 2.5 micrometers.


Unltrafine particles.


Particles measuring 2.5µm or less. These are the fraction of the particulates which are thought to be the most dangerous.

EU has a PM2.5 limit of 25µg/m3 averaged over 1 year. These limits are reducing to 18µg/m3 averaged over 3 years by 2020


Particles measuring 10µm or less. Due to their size they are readily inhaled and are not filtered. They penetrate deep into the cardiovascular system where they cause damage.

Ultrafine Particles

EPA classification of particles having aerodynamic diameters less than or equal to 0.1 micrometer.

See also: Aerosol, Air Toxics, Diesel Particulate Filter, Dispersion Model, Inertial Impaction, Mass Median Particle Diameter, Smog, Toxic Emission.

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Subjects: Automotive Chemistry Environmental

EU Air Quality Standards Summary of the European Union body of legislation which establishes health based standards and objectives for a number of pollutants in air.