Understanding Air Filter Classification

Air filters are used in many different settings, from homes and offices to industrial facilities and hospitals. They are designed to protect the system from the accumulation of dust and particles that could cause damage, as well as improve indoor air quality by removing dust, pollen, pet dander and other undesirable particles. Air filters are rated according to their MERV ratings, with a higher number representing better filtration. Filter efficiency (air filter grade) is reported as a percentage (50% to 95% in 5% increments) for each of the above EPm ranges.

For example, if an air filter is classified as ePM1 %3D 70%, the filter has been tested and is known to remove 70% of particles in the 0.3 - 1 μm size range. In Europe, EPA, HEPA and ULPA filters are subject to EN 1822 classification for filtration efficiency and zero leakage. The international standard ISO 29463 is based on this European standard and, in the meantime, has replaced it in essential parts. Filter tests are based on high-precision particle counting methods. In industrial facilities, air filters preserve the quality of products and materials and protect critical equipment from damage.

Therefore, their higher density of filter media reduces airflow; this results in higher energy consumption than HEPA filters. According to MIL-STD-282, to be considered a true HEPA filter, the filter must capture at least 99.97% of airborne particles with a diameter of 0.3 microns. In an ionizing air filter, dirty air passes first through a pre-filter and then through an ionizer to give airborne particles an electrical charge. Foam air filters are made of porous foams designed made of polyurethane, polyether, polyester or a combination of those materials. Aluminum air filters have high strength and durability and can be washed or cleaned and reused several times. ISO coarse gravimetric filter arrest for filters that cannot achieve a minimum efficiency of 50% in EPM10. With the revised ISO 29461 Part 1 test standard, a new classification system for air filters in turbomachinery intake filtration comes into effect.

Dust holding capacity is the average weight of dust that an air filter can retain when loaded with synthetic dust incrementally under specified test conditions. In general, filters with a MERV 16 rating or lower are considered HVAC system grade filters for residential, commercial, and general hospital use. When used in a multi-filter system, pre-filters trap dirt and large particles before the air reaches the final filters downstream, which then remove smaller particles. UV air filters kill bacteria, viruses, molds and other pathogens by destroying your DNA using powerful short-wave ultraviolet light.