Air conditioners with HEPA filter

HEPA filter

— a special kind of mechanical fine filter.

The action of HEPA filters is based on the use of microscopic channels of a special shape — with pockets and branches. When air is passed through such channels, relatively large particles simply get stuck, while small ones, by inertia, fall into the pockets and remain there. Thanks to this, HEPA filters can retain contaminants, the size of which is noticeably smaller than the actual diameter of the channels. The effectiveness of such elements is evaluated by the ability to filter out particles with a size of 0.1 – 0.3 microns (a thousandth of a millimetre) since it is these microparticles that are the worst retained by the filter (they are smaller than the diameter of the channels and at the same time large for branches). Based on this, HEPA filters are assigned classes, nowadays the following options are relevant:

— class 10 – traps at least 85% of the particles mentioned;
— class 11 – not less than 95%;
— class 12 – not less than 99.5%;
— class 13 – not less than 99.95%;
— class 14 – not less than 99.995%.

Accordingly, other contaminants (including smaller ones) are retained by such filters even more efficiently. For comparison: the size of most bacteria is 0.5 microns or more. So anyway, the presence of a HEPA filter indicates a high efficiency of fine cleaning.