From G1 to U17: classification of air filters by the degree of air purification

Air filters are commonly used to maintain the required air purity in the serviced premises. In domestic ventilation systems, filtration is necessary to protect an apartment or house from dust particles and various impurities. In industry and in food production, the requirements for filtration systems are fundamentally different. For example, at a cement factory, filters are required to effectively eliminate coarse dust particles, and in a sterile operating room, they are expected to completely clean the air masses.

International standards divide filters into four classes, which are determined by the level of air filtration. The fundamental documents in this area are the EN 779:2012, DIN 24184 / 2185 standards. Industry standards in other countries are also “written” on their basis. Each class of filters has its own area of responsibility in ventilation, recuperation and air purification systems:

1. G1 – G4 (EU1 – EU4) – coarse filters.

Filters of G1 – G4 classes capture the largest pollution: from 60 to 90% of large synthetic particles larger than 0.4 µm. They are most often used as pre-filters and in rooms with low requirements for air purity.

Coarse filters G1 – G4 come in a variety of shapes and sizes.

Usually coarse filters have a primitive design; they can be made of a thin sponge or mesh with different cell sizes. Fine dust fractions and harmful gases easily pass through them, but poplar fluff, animal hair, insects, coarse dust and plant seeds are effectively retained. For G-class products, the layers of the filter sheet are relatively loose so that the filter does not clog excessively and that there are no obstacles in the way of air flow

2. F5 – F9 (EU5 – EU9) – fine filters.

Finer air purification is performed by filters of F5 – F9 classes. They are able to hold up to 75% of particles smaller than 0.4 µm. Filters of this class are installed as the second stage of air purification in household or industrial ventilation systems.

The pocket form factor is the most common in the fine air filter category.

Many of the F-class filters are not structurally different from the G-class products. The difference is the higher density of the material used for filtration. The most widely used are fine pocket filters made of polyester or polypropylene fibers. Closer to the 9th digit, the filters become similar to multi-layer HEPA cartridges, but more on that below. Air filters F5 – F9 trap medium and fine dust, fluff, pollen from some plants, fungal spores and molds. The areas of their application are the most extensive – from private households to food production.

3. H10 – H14 (HEPA 10 – HEPA 14) – high efficiency filters.

HEPA is an abbreviation for High Efficiency Particulate Absorption. HEPA filters are designed for complex air purification. They hold up to 99.995% of all particles larger than 0.3 µm. Air purifiers based on HEPA filters are used in medical institutions, clean rooms, as "finishing" elements of advanced filtration systems, recommended for allergy sufferers and little children.

Due to the high efficiency of air purification, HEPA filters have begun to be massively introduced into the design of vacuum cleaners.

HEPA filters are made from a folded sheet of fibrous material (fiberglass). This sheet is placed in a metal or plastic case. Products from this family are adapted to filter the air from the slightest pollution that is significant for human health. They effectively trap dust, dangerous viruses and bacteria, plant pollen and other allergens.

HEPA filters need to be changed regularly: at least once a year. In fact, the timing of replacement depends on the degree of contamination of the air and the condition of the pre-filters in the ventilation or recuperation system, in the air purifier. HEPA filters with clean pores remove all fine dust and allergens from the air most effectively.

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4. U15 – U17 (ULPA15 – ULPA17) – ultra high efficiency filters.

ULPA class filters have a number of specific tasks to maintain absolute purity of the air. Their name means Ultra-Low Particulate Air. Filtration efficiency ranges from 99.9995% to 99.9999995% with slippage from 0.0005% to 0.000005%. Ultra-high purification efficiency filters are used in nanolaboratories, nuclear power plants, and hospital operating rooms. In everyday life, they are practically not found (with the rarest exceptions).

ULPA class filters are intended for absolutely "clean" rooms.

ULPA filters are niche products aimed at a narrow audience. They can be found in ventilation and air purification systems for rooms with the highest requirements for air purity.

The filter class is determined by the efficiency of cleaning the air masses. The higher it is, the finer air purification the filter produces. And the less dangerous and harmful particles will enter the human lungs with every full-bodied breath.