What Is a HEPA Filter?

What Is a HEPA Filter?

June 10, 2019

The HEPA air filter has been used for decades, having first been developed during World War II by the federal government to be an effective gas mask for the troops. Since then, the filter has been used in all types of settings, including medical and industrial, to remove particulates from the air.

To fit the qualifications of a HEPA filter, it must remove at least 99.97 percent of airborne particles that are at least 0.3 microns in size. Any filter that does not meet those requirements is not a true HEPA filter. A micron is another term for a micrometer, or one millionth of a meter (compare to a millimeter, which is one thousandth of a meter). These are particles you cannot see with the naked eye.

Here’s a bit of information about HEPA filters from our air purification company.


You’ll find HEPA filters available in two different types of materials: fiberglass and nonwoven fabric.

Fiberglass filters achieve HEPA performance or better, and have the highest filter efficiencies. However, it’s also worth noting that they have the highest airflow resistance (also known as pressure drop). Nonwoven fabric materials (typically polypropylene) are able to achieve better than HEPA standards with a lower pressure drop than you’d find in fiberglass filters, meaning better air filtration as a result.


The biggest benefit of HEPA filters is just how effective they are at removing particles from the air. The 99.97 percent removal rate is a standard set by the U.S. Department of Energy. While it might not sound like it, there’s a big difference in 99 percent efficiency and 99.7 percent efficiency, with the ability to remove many more of the tiniest particles. The ability to remove these very small particles effectively is critical, because the smaller particles are the ones that tend to pose a greater threat to your lungs. They’re too small to be captured by the mucus membranes in your nasal system, so they go straight through to your respiratory system. They can then enter your bloodstream and cause further issues.

There are, however, some limitations to HEPA filters, as efficient and effective as they are. Keep in mind that these filters are designed to remove airborne particles. What they do not help with is gas or odor. So, for example, a HEPA filter may help you remove the tobacco particles from cigarettes that are in the air in a particular area, but it won’t do anything about the resulting smell from smoking.

Gases cannot be trapped by the filters because they are much, much smaller than particles floating in the air.

All that being said, HEPA filters are great purifiers for allergies and asthma, and are excellent to have in workshops and industrial areas, but it’s important to know their limitations as well.

For more information about HEPA filters and air purification, we encourage you to get in touch with the team at AAir Purification Systems today. We’d be happy to tell you more about our products and systems!

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