Everything You MUST Know about HEPA Filters

Miele HEPA FilterOne of the best things you can do to help keep allergies at bay is to use vacuum cleaners and air purifiers with HEPA filtration. But different manufacturers use different terminology to say, essentially the same thing, so comparing one product to another isn’t always as straightforward as it should be.

There’s the HEPA filter, and then there are variations on the HEPA filter, as well as ULPA and HEGA filters and a few things in between. There’s a lot of information available about the underlying technologies and how they relate to vacuum cleaners and air purifiers, including articles in our own library, but there are only a few things you absolutely must know about filters before you start shopping:

HEPA Filtration

HEPA stands for High Efficiency Particulate Air. A HEPA filter must remove 99.97% of all particles as small as 0.3 microns in size from the air that passes through it. This is the standard “best” filtration method for residential and most commercial applications.

The phrase “as small as” is important because it designates that if all the particles were 0.3 microns in size, the filter would still have 99.97% efficiency. The term “down to 0.3 microns in size” does not refer to the same filtration performance as it may refer to a mixture of particle sizes for the stated efficiency.

You may see terms such as “Certified HEPA,” “True HEPA” or “Absolute HEPA.” These all are HEPA filters that meet the same HEPA standard. Where you need to be careful is when you see terms such as “HEPA-like” or “HEPA quality” or any other qualification that is used where you expect to see “HEPA”.


HEPA is used primarily in the United States. In Europe, companies generally refer to the same filter as an S-Class filter and some manufacturers, like SEBO, use the terminology here. Like HEPA filters, S-Class filters must remove 99.97% of all particles as small as 0.3 microns in size from the air that passes through them.

Active HEPA Filter

This is a Miele trade name for a HEPA filter that incorporates an additional charcoal filter to help absorb odors.

HEPASilent Filter

This is a Blueair trademark for technology that combines a HEPA filter with an electrostatic filter. While this may allow the HEPASilent filter to trap and hold particles with greater efficiency, it does not necessarily provide better performance than a standard HEPA filter.

HEGA Filter

This is an Austin Air trade name that stands for High Efficiency Gas Adsorption filtration. This is HEPA filtration combined with an Activated Military Carbon Cloth filter to remove a wide variety of odors and gasses.


UPLA stands for Ultra Low Penetration Air and is significantly more efficient than HEPA, removing remove 99.999% of all particles as small as .12 microns in size from the air that passes through it. It is used in clean rooms, labs, hazardous materials clean-up and other environments where the highest levels of filtration must be utilized.

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