Air purity targets

The basis for the choice of filter is the desired level of indoor air purity. The level of filtering is determined according to the filtering needs imposed by the functions of the site, production process, end product, facility or atmospheric purity, and ventilation system protection.

Impurities in the outdoor air

The choice of filter is also affected by the nature of the air being filtered. For filtering, the essential question is the particle level in the air to be filtered and the distribution of particles.  If there are gaseous impurities in the outdoor air, such as might be expected in urban or industrial areas, a chemical filter is required in addition to the particle filter.
 
Recommended filter classes and operating instructions

The desired indoor air purity in buildings is usually attained with fine filters (F7 and F8). These classes are common for sites where people work or spend time. They separate out the majority of staining particles as well as dust and spores that are harmful to the lungs.  Coarse mesh filters (G3–F5) are often used as the primary filter system before the fine filters and also in warehouses.

Examples of recommended filtering classes:

• Residential buildings F7
• Office buildings F7
• Schools and libraries F7–F8
• Day care facilities F8 
• Hotels and restaurants F7–F8 
• Hospitals (corridors and rooms) F8–F9
• Operating rooms, instrument cleaning H10–H14
• Industrial clean rooms U15–U17