Particulate matter filters

How do PM filters work?

In the case of highest air purity requirements, high-efficiency particulate air filters (alternatively named particle filters) are used to remove aerosols and toxic dusts. The filter classes H13 and H14 are comparable with the separation efficiency of dust class H.

In Europe, the classification of particle filters in ventilation systems is currently in accordance with the norm DIN EN 779. In July 2018, the ISO 16890 will come into force as a replacement. The four filter groups of this new international standard are based on the particle size of the dusts:

ISO Coarse (based on the retention of ISO A2-dust)
ISO PM10: particulate matter ≤ 10 μm
ISO PM2.5: particulate matter ≤ 2.5 μm
ISO PM1: particulate matter ≤ 1 µm

For effective separation, the European standard EN 1822-1: 2009 classifies particulate air filters into filter classes E10-E12 (EPA), H13-H14 (HEPA) and U15-U17 (ULPA). The "High Efficiency Particulate Air Filters" ((H) EPA) are classified according to their respective degree of separation. Its surface consists of up to 1,000 layers of close-meshed cellulose and synthetic fibers. The size ensures a higher filter efficiency for fine dust, suspended particles and very small particles. With a degree of separation in the range of 0.1-0.3 μm of > 99.9 percentage, less than three out of 10,000 particles thus remain. Regular change intervals prevent the emergence of germs and bacteria, which can occur at high pollutant concentration in saturated filters. In the USA, HEPA filters have a fixed degree of separation and are comparable to the filter class H13 according to EN 1822-1.

A vacuum cleaner can only draw in deposited air from a surface. The particles are recognizable on it, as well as a weakened suction power. Extraction systems draw in and filter the contaminated air, and are therefore more effective. They safely suck in not only deposited particles, but also those floating in the air. The dust classes categorize all systems.

In dust-prone processes, the employee does not necessarily perceive the high load on his ambient air, since the smallest particles float airborne and are invisible to the human eye. For this reason, every extraction system requires an optical or audible warning signal if the suction power decreases. Because in this case, the employee would no longer be optimally protected.

Most technical rules and standards assign to the following technical protection measurements for dust-emitting processes: avoidance, direct exhaust at the point of emission, ventilation measurements and personal protective equipment. Effective detection of dusts at the point of origin is therefore one of the most important protective measurements taken by the employees.