History
The name HEPA stands for High Efficiency Particulate Air. The first idea behind the development of HEPA filter goes back to German soldiers during WW II, who were wearing gasmasks with inserted paper showing a remarkably high capture efficiency for chemical smoke. In the 1950 after a number of development stages the HEPA Filter was commercialised.

What is HEPA?
HEPA is a standard for filters as defined by the United States Department of Energy and in Europe by the European Standard EN 1822-1:2009. HEPA Filters are separated in several classes of efficiency. HEPA H13 and HEPA H14 are within the highest tier of HEPA and are considered medical grade Filters. ETS Air Disinfection Devices are equipped with HEPA H13 Filters which remove at least 99.95% of airborne particles 0.3 micrometers (μm) in diameter.

Caution: HEPA versus HEPA Type or HEPA Like
There are NO different Types of HEPA filters, as filters either meet of fail the norm in order to be called HEPA. The Term HEPA “Type”, HEPA “Style” or HEPA “Like” as advertised by many market participants is misleading, has no legal meaning and essentially is scientifically meaningless yet dangerous, since it insinuates safety and high level standards, which is not the case. The efficacy of such HEPA Type or HEPA Like filters do not meet the HEPA standards and may not have been tested.