Particulate matter and ISO 16890 air filter standards define efficiency classification

The effects of particulate matter (PM) on human health have been extensively studied in the past decade. The results are that fine dust can be a health hazard, contributing to or even causing respiratory and cardiovascular diseases.

The different classes of particulate matter are defined according to the particle size. The most important ones are PM10, PM2.5 and PM1.  The U.S. Environmental Protection Agency (EPA), the World Health Organization (WHO) and the European Union define PM10 as a particulate matter which passes through a size-selective inlet with a 50 percent efficiency cut-off at 10 µm aerodynamic diameter. PM2.5 and PM1 are similarly defined. However, this definition is not precise if there is no further characterisation of the sampling method and the sampling inlet with a clearly defined separation curve.

The reference method for ‘sampling and measurement’ of PM10 is described in EN 12341 in Europe. The measurement principle is based on a filter of the PM10 fraction of ambient particulate matter and the gravimetric mass determination ( EU Council Directive 1999/30/EC of 22 April 1999).

As the precise definition of PM10, PM2,5 and PM1 is quite complex and not simple to measure, public authorities, like the U.S. EPA or the German Federal Environmental Agency (Umweltbundesamt), increasingly use in their publications the more simple denotation of PM10 as being the particle size fraction less or equal to 10 µm. Since this deviation from the above-mentioned complex ‘official’ definition does not have a significant impact on a filter element’s particle removal efficiency, the ISO 16890 series refers to this simplified definition of PM10, PM2,5 and PM1.

Particulate matter in the context of the ISO 16890 series describes a size fraction of the natural aerosol (liquid and solid particles) suspended in ambient air. The symbol ePMx describes the efficiency of an air-cleaning device to particles with an optical diameter between 0,3 µm and x µm. The following particle size ranges are used in the ISO 16890 series for the listed efficiency values.

ISO 16890 series

The ISO 16890 series describes the equipment, materials, technical specifications, qualifications and to produce laboratory performance data. It also defines efficiency classification based on the measured fractional efficiency converted into a particulate matter efficiency (ePM) reporting system.

In accordance with the ISO 16890 series, air filter elements are evaluated in the laboratory by their ability to remove aerosol particulates – expressed as the efficiency values ePM1, ePM2,5 and ePM10. The air filter elements can be classified according to the procedures defined in this part of ISO 16890. Particulate removal efficiency of the filter element is measured as a function of the particle size in the range of 0,3 µm to 10 µm of the unloaded and unconditioned filter element as per the procedures defined in ISO 16890-2.