View source for PM2.5

=== '''Definition''' ===

PM2.5 particles are those with diameters of less than 2.5 micrometres*. They are therefore a subset of PM10 particles and more harmful than PM10, as they can reach further into the lungs and can be more toxic.

PM2.5 particles are usually composed mainly of secondary particles formed in the atmosphere from some of the gaseous precursors.

=== '''Legislation and intervals''' ===

According to World Health Organization: The limit value for PM2.5 is 15 μg/m3 for 24 hours and 5 μg/m3 on an annual average.

According to DIRECTIVE 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe: The limit value for PM2.5  is 20 μg/m3 on an annual average.
[[Category: Indoor air pollutants]]