The True HEPA Filter Revealed

Only in air purifier marketing will you see the term hyped as if it were the all-important gold standard. This is not necessarily a bad thing. Air purifier companies have one very good reason for it – Shady competitors with inferior products dishonestly associate themselves with the HEPA efficiency standard.

The term true HEPA is entirely a marketing term. In industry, government and military applications a filter is either HEPA or it isn’t. However, there are different specifications for defining HEPA.

Defining The True HEPA Filter Standard

The European Standard EN1822-1 defines a HEPA filter as ranging from 85% to 99.995% efficient against a 0.3-micron challenge. However, there are specific filtration grades given to each filter spanning that range. This allows an end user to know exactly what they are purchasing. In many respects, it is a better way of expressing air filter efficiencies.

How Other Filters Compare To True HEPA

A True HEPA filter's D.O.P.-rated efficiency is it’s minimum starting efficiency. The actual operating efficiency is higher than that, for all particle sizes from 0.001 micron upwards.

The starting efficiency of any non-HEPA air cleaner is very much lower – anywhere from 5% to 60% by the D.O.P. test. True HEPA filters are far more efficient for air cleaning than other types of filtration systems.

Filter systems like electronic air cleaners' aluminum plates or 3M Filtrete media depend on electrostatic charges to attract dust to its plates or fibers. As the plates or fibers load up with dust, their ability to attract more dust drops dramatically.

An electronic air cleaner or 3M Filtrete-based air cleaner's starting efficiency is usually the maximum efficiency. With use the efficiency will drop very fast and the average operating efficiency is much lower.

Some published studies have shown that an electronic air cleaner's efficiency can drop to one-fifth of its starting efficiency within 26 hours of operation. That, plus the fact that most electronic filters are not very efficient at .3 microns and even worse for particles less than .3 microns, makes a strong case against electronic filter types.

A Few Facts About True HEPA

True HEPA filtration is currently the only type of air purification recommended by the U.S. Government’s Department of Homeland Security and FEMA.

Contrary to the claims of misleading air cleaner ads, bacteria and viruses do not breed in true HEPA filters. HEPA filters provide a dry environment and without moisture there is nothing to keep bacteria alive, much less breed. These trapped contaminants eventually die from lack of moisture. This is why only true HEPA filters are used where health is critical as in hospital operating rooms and ICU wards. Bacteria can breed within the filter only if the air coming into the filter is moist. If such is the case, methods for killing bacteria within a HEPA filter include antimicrobial treatment of the media or a germicidal ultraviolet light.

Though it may only be a marketing term, it is born of the necessity to counteract the efforts of many impersonators. There are many air cleaners claiming to have HEPA type filters. These air cleaners have no specified performance rating, so you have no way of knowing how good it is. In many cases a high efficiency furnace filter with a MERV 13 rating would be as good as these much more expensive air cleaners.

My own personal conviction is that buying a HEPA filter air purifier is the best choice I can make.