Until July 2018, the classification of air filtration was based on the well-known DIN EN 779:2012 standard. However, after many years, it has lived to see its replacement and has been superseded by a new, more precise one – DIN EN ISO 16890. This norm marked a new stage of development and changed the standard classification of filters according to classes G, M and F by implementing ePM classes.
Classification according to the ISO 16890 standard
The introduction of the new ISO 16890 standard made it possible to examine the actual evaluation of filter performance. For this purpose, the suitability of the filter is measured according to different particle sizes from 0.3 μm to 10 μm, and not just 0.4 μm (with the use of synthetic ASHRAE test dust) as was the case in EN 779:2012. With the new standard, a more reliable and accurate description of the actual filter performance is possible and thus the filter can be selected precisely according to the requirements.
Coarse and fine dust filters are divided into four groups, but the determining factor is whether the filter can separate more than 50% of the relevant particle size range. If the filter does not achieve 50% efficiency in any of the PM fractions, then it is given a filtration class in the Coarse group (coarse filter).
If the filter captures more than 50% of the ePM1 particles, it will be assigned to the ePM1 filter group according to ISO. The corresponding efficiency is then given to the nearest 5%. These are indicated from 50-95%. Despite the fact that one filter can have two or three filtration classes according to the new standard, we give only the one selected.
Filter testing procedure according to ISO 16890
In the standard EN 779, a sample of the filter medium was dipped in isopropanol, then dried and tested for filtration efficiency of 0.4 μm particles. The purpose of using isopropanol was to neutralize electrostatic charges on the fibers. According to the new ISO 16890 standard, not only the pure filter medium is discharged in isopropyl fluide, but the entire filter is subjected to isopropanol evaporation (ISO-steam) for 24 hours. In this way, the effect of electrostatic charge is eliminated.
The procedure begins by measuring the fractional efficiency curve with an air filter in the particle size range of 0.3 to 10 microns. To test the air filters as realistically as possible, the filter is electrostatically discharged before the separation efficiency and differential pressure are measured again. The filter is then exposed to a vaporized atmosphere of isopropanol to assess the extent to which particle collection is based on electrostatic mechanisms. Next the particle efficiency curve is measured again. The efficiency classification is calculated from the average of the initial efficiency and also from the initial efficiency after discharge.
The efficiency increase ePM1 is calculated for the particle size range up to 1 micron, ePM2.5 for the particle size range up to 2.5 microns and ePM10 for the particle size range up to 10 microns.
Did you know that…?
A person inhales about 15 kg of air per day, while in comparison, they consume about 1 kg of food and drink about 2 kg? In particularly contaminated areas, humans are exposed to 25 million dust particles with every breath.