Will changing the filtration class from G4 (ISO Coarse) to F7 (ePM2.5) result in better protection against pollution? Let’s start by explaining what are filters in class G4 (ISO Coarse) and F7 (ePM2.5) and what are their main tasks?
The G4 (ISO Coarse) filter is also called a pre-filter, which means that in HVAC systems it is installed first at the inlet and this filter is also the first to come into contact with air that is taken in from the outside. As we know very well, the air that is outside and goes directly to ventilation systems is very polluted. Contaminants include elements such as leaves, pollen from trees, small insects, solid particles, fungi, molds, bacteria, and viruses.

The main task of the first G4 (ISO Corse) filter that is in our sequence is to capture the largest impurities that can be seen with the naked eye, i.e. leaves, insects, or pollen from trees. Another filter in our sequence that is installed in the HVAC installation is the F7 (ePM2.5) or F9 (ePM1.0) fine filter. The purpose of this filter is to capture particles that are not visible to the naked eye and go through the nose, mouth, throat of the lungs into our bloodstream. Appropriate filter construction, starting from the material structure, e.g. pocket length in the case of a pocket filter or the size, thickness, and the number of pleats in the case of a cassette filter, stops these harmful to human impurities.

Answering the question that we asked ourselves at the beginning of the article, we should think about what will happen to our fine filter if we mount it at the beginning of the sequence and then in the second stage we also mount the fine filter?

As the structure of the filter material with a higher class F7 (ePM2.5) or F9 (ePM1.0) is more accurate, it catches any dirt better. If we install this type of filter at the inlet to our section, it will certainly stop all large and small impurities, but what will happen to our filter if after a few days of “hard and accurate work” of collecting leaves and pollen from trees? The filter will contaminate to such an extent that the pressure drop point increases very much, which means that the HVAC system will be forced to work intensively with higher consumption of electricity. For this reason, we do not recommend replacing the filters from G4 (ISO Coarse) with F7 (ePM2.5) or F9 (ePM1.0) during the initial filtration phase because it will be necessary to increase the frequency of replacement of the pre-filters.