How do filters differentiate in performance, where do filter names come from, and what can I see in them?
Air filters are essential elements in ventilation and air-conditioning systems to ensure good indoor air quality and system hygiene. Since 01.07.2018, the testing standards and the qualifications of air filters have changed from EN 779 to ISO 16890.
The new ISO 16890, unlike EN 779, evaluates the effectiveness of air filters against the different particulate matter fractions PM1, PM2.5, PM10 and Coarse (fine dust up to 1μm, up to 2.5 μm, up to 10 μm and coarse dust). These PM (Particulate Matter) fine dust values are also used analogously in the evaluation of outdoor air quality. A filter can therefore be selected to match the existing outside air quality.
The filter class groups ISO ePM1, ISO ePM2.5, ISO ePM10, and coarse dust with ISO coarse have replaced the previous filter classes G1 to F9. With the new test standard and its classification system, operators and planners of ventilation and air-conditioning systems can select filter solutions that meet their needs much more easily than with EN 779:2012. In the new testing and classification procedure, the separation behavior is determined with regard to all particle sizes between 0.3 and 10 µm occurring in the outside air, instead of exclusively with particles of size 0.4µm, as was previously the case. This means that the standard is more closely aligned with real-life operating conditions.
When selecting filters in relation to the desired air quality, the new group classification is much more user-friendly. There are four filter groups for which an identification requirement is given with the percentage collection efficiency of the filter in the associated spectrum.
Example: Class ISO ePM1 75% has a collection efficiency (e) against particles ≤ 1 µm of min. 75%. Filters whose collection efficiency is lower than 50% for PM10 are assigned to ISO coarse dust filters.
| Class | Efficiency range | Example particles / fine dust |
| ISO ePM1 | ePM1.min >= 50% | viruses, bacteria, nanoparticles, soot (from fossil fuels), sea salt, oil mist |
| ISO ePM2,5 | ePM2.5,min >= 50% | bacteria, fungal & mold spores, pollen, toner dust |
| ISO ePM10 | ePM10 >= 50% | pollen, rock dust, dust from field cultivation |
| ISO Coarse | ePM10 <50% | sand, lint, flying seedlings, hair, etc. |
The human body absorbs a variety of particles and dusts through the air we breathe. In particular, small particle fractions make up the majority of these particles and can reach the blood and organs via the alveoli. Filters within the scope of ISO 16890 reduce particle quantities in the range >0.3 µm by up to >90%.
A large number of directives, standards and regulations refer to the filter classification of EN 779 and will probably only be able to be successively over the next few years. Therefore, the question of comparability increasingly arises when air filters with a new classification are used.
A simple justified translation from old to new classes fails because of the different evaluation methodology. A correct translation must be made in the future in the respective application standard for the filters.
Orientation guide for comparison of filter classes old and new:
| EN 779: 2012 | ePM 1 | ePM 2,5 | ePM 10 |
| M5 | 5% - 35% | 10% - 45% | 40% - 70% |
| M6 | 10% - 40% | 20% - 50% | 60% - 80% |
| F7 | 40% - 65% | 65% - 75% | 80% - 90% |
| F8 | 65% - 90% | 75% - 95% | 90% - >95% |
| F9 | 80% - 90% | 85% - 95% | 90% - >95% |
