The main purpose of filters of air handling units is to protect its internal components from contamination by particles and to supply healthy air into the premises. Ventilation filters are classified according to ISO 16890 standard into 4 categories: ePM1 (captures PM1 particles by higher efficiency than 50%), ePM2.5 (captures PM2.5 particles by higher efficiency than 50%), ePM10 (captures PM10 particles by higher efficiency than 50%), %), Coarse (captures PM10 particles by lower efficiency than 50%).
Filters are being tested with a special mixture of particles in specialized laboratories to determine their efficiency (so-called tested filters). It is worth to mention, that tests are costly and most of “cheap” filters manufacturers and distributors (quite a lot of them from China, Turkey, etc.), just provide calculated data according to filtering material they are using.
ePM1 class filters capture the most dangerous particles, of dimensions 0.3-1 microns (µm). For example, CleanFiler filter ePM1 70% (ex. F7 class) captures event 70% of such particles. Therefore, it effectively protects from allergens, even form some smog particles (0.001-1µm). But general ventilation filters are not designed from the smallest microorganisms, such as bacteria or viruses. In fact, even most of the ventilation units are not designed for such purposes. Despite it, some manufacturers or distributors started marketing such filters for protection from viruses…
The size of Coronavirus is between 120-160 nm or 0.12-0.16 µm, therefore ePM1 class filters cannot capture the virus itself. For filtration of viruses and bacteria are dedicated EPA/HEPA filters, which can contain up to 99.995% of 0.3µm particles. But the pressure drop of such filters is quite high (pressure drop is 2 times higher than ePM1 filter), therefore there is no reason to install it to the residential air handling unit. In order to protect fully from microorganisms also UV lamps are being used in ventilation systems. For the protection from microorganisms’ special units are designed for such applications as laboratories, hospitals, etc. They differ in their construction, materials from standard ventilation units.
COVID-19 transmits through the sneezing particles. Scientists have determined the size of such particles during the tests. The size variates from 0.35 up to 2.5µm. 38.3% of them are of size 0.8-2.5 µ and can be captured by ePM1 class filters, but most of them will not be captured.
It is also worth mentioning that the probability of Coronavirus entering through the house ventilation system is quite low because the air intake is usually quite far from potential source – sick person.
Nevertheless, efficient air filtration captures dangerous particles, which can pass into blood vessels and influence cancer development, cardiovascular diseases or even dementia. Allergic particles can weaken the immune system of susceptible people and make them more vulnerable to infections.
In each case, select the filter according to your sensitivity and environment. This will help to create a clean indoor climate for a healthier life.