PM10 is particulate matter which passes through a size-selective inlet as defined in the reference method for the sampling and measurement of PM10, EN 12341, with a 50 % efficiency cut-off at 10 µm aerodynamic diameter.
PM2.5 is particulate matter which passes through a size-selective inlet as defined in the reference method for the sampling and measurement of PM2,5, EN 14907, with a 50 % efficiency cut-off at 2,5 µm aerodynamic diameter.
A portion of matter is an aggregate of material entities that have a state of matter.
Editor note:
Portions of matter describe mass nouns like e.g. water, air and fuel. Mass nouns are uncountable, but portions of these can be quantified, like 1 glass of water, 1 m³ of air or 1 barrel of fuel. For further explanation please refer to: https://github.com/OpenEnergyPlatform/ontology/wiki/Explanation-on-mass-nouns
Ontology