Air filtration is very important part of any ventilation system. Every year, level of environmental pollution is growing and the need for quality filtration is also increasing.

Our company develops projects and installs ventilation systems with maximum degree of air purification for objects such as laboratories, pharmaceutical enterprises, surgical rooms and other facilities where “clean rooms” are needed.

Classification of air filters is very difficult to understand for a simple person. In this article, we will try to tell you about it as simply and easily as possible.


Classification of air filters

Action effectiveness, air filters are divided into 3 or 4 categories, depending on their filtering abilities.

1. Filters for rough cleaning. Used in rooms with low requirements for clean air or as one of the stages of air purification – air pre-purification. Such filters capture large particles with a size of 10 microns.

! Μicron is a measure of small distances length, 1 micron = 0.001 mm = 0.0001 sm = 0.000001 m. For example, the erythrocyte diameter is 7 microns, atmospheric particles mostly have a diameter from 0.1 to 5 microns.

1. Fine air purification filters. They are used practically in all areas of industry or in everyday life, as a rule they are installed as a second stage of air purification. Different particles larger than 1 micron are trapped.

2. Absolute air purification filters or HEPA filters. Such filters are used to create “clean rooms” in pharmaceutical companies, operating companies, electronics industry and other areas where a high level of filtration and particle size removes from 0.3 micron  is required. Until now, these filters were the most effective filters.

3. ULTRA filters – are the fourth kind of filters which has not become a separate type of filtration yet, someone still divides all filters into three types, classifying Ultra filters as absolute air purification class, and somebody allocates ultrahigh-purity filters to a separate class. These are final air purification filters and are used exclusively in specialized rooms in which the most effective air filtration is needed.

Filters marking depending on filtration class

Each of the above categories has several classes of cleaning. Which are called differently depending on standard.

Table 1 shows marking of filters, depending on the class of their effectiveness.

Level of cleaning Type of cleaning Cleaning efficiency, %
DIN 24184 DIN 24185 State standard Р 51251-99 EN 779 EN 1822 State standard Р 51251-99 EN 1822
    According to test methods*
      Ee      Ea E O
Rough EU1 G1 G1   J60     J65
EU2 G2         G2   6070     6580 <20
EU3 G3         G3   7080     8090 2035
EU4 G4         G4   8090     9095 3545
Fine EU5 F5         F5   9095     4560 <20
EU6 F6         F6   9597     6080 60
EU7 F7 F7   9798     8090 45
EU8 F8         F8   9899     9095 60
EU9 F9 F9   99,8     9598       75
High efficiency (НЕРА) H10 H10 85
H11 H11 95
H12 H12 99,5
H13 H13 99,95
H14 H14 99,995
 Ultra-high (ULPA) U15 U15 99,9995
U16 U16 99,99995
U17 U17  99,999995
Table 1. Classification and marking of air filters. Note: EN779 and EN1882 are Russian standards for raw, fine and ultra fine filters, respectively.