What is HEPA? 

What is HEPA filter

If you research air cleaning technologies or the quality of air inside your home or office worries you, you’ve probably heard of HEPA. If you suffer from asthma or allergies you may be familiar with the term. However, if you are new to indoor air quality issues, you may wonder, What is HEPA? 

HEPA stands for High-Efficiency Particulate Air. It’s a standard for clean air and has been around for decades. However, more recently it has entered the commercial space. It’s a common feature for air purifiers.

What is a HEPA Filter?

The HEPA standard was created in the 1940s but the certification process wasn’t used until 1983. In the years following WWII, fears of contamination caused by nuclear testing prompted the U.S. Department of Energy to set the standard. It served as a form of protection against radioactive particles. Today, the HEPA standard helps air purifiers clean the air in homes and offices. 

To be labeled a HEPA filter, it must remove a minimum of 99.97 percent of all particles 0.3 microns in diameter. While too small to see with the naked eye, these particles impact health. When you shop for air purifiers you may notice alternate HEPA labels. Pay attention to the wording because this could be marketing language. Some air purifiers use language like “HEPA type” filters, however, this does not mean they meet the standard. A product may also describe its filter as “HEPA-like.” These low-quality filters also do not meet the standard. A filter is either HEPA or it isn’t. 

You may also see marketing language such as “Ultra HEPA” or “True HEPA”. The latter is sometimes used to set the American and European standards apart. For a filter to receive certification in Europe it need only capture 85 percent of all particles 0.3 microns or larger.

What Does the HEPA Filter Rating Mean?

To get the best performance out of air cleaning technology, in other words, the cleanest air, look for the purifier with a high-rated HEPA filter. The higher the grade of the HEPA filter the better it filters particles. For example, a True HEPA filter has a rating of H10-H12. These filters trap between 85 and 99.5 percent of particles 0.1 microns in diameter. However, a HEPA H13-H14 traps between 99.95 and 99.995 percent of particles. Both of these types are commercial-grade filters. 

Medical-grade HEPA filters provide the highest level of filtration. The construction of the filter includes densely packed fibers. These fibers trap the tiniest of particles.

Dyson HP04 Tower Pure Hot Cool Air Purifier
The Dyson HP04 Tower Pure Hot Cool Air Purifier features a HEPA filter.

How Do HEPA Filters Work?

Most filters made for modern air purifiers consist of interwoven glass fibers. These fibers stop particles in the following four ways: 

1. Direct Impaction 

This is when particles lodge themselves in the glass fibers. Unable to move forward, they cannot re-enter the room.

2. Sieving 

This occurs as the particle moves through the filter. It may pass partially through, but eventually becomes stuck between two fibers and cannot move forward.

3. Interception

Even when the airflow moves particles around fibers, the density of the fibers stops its motion thus preventing it from leaving the filter.

4. Diffusion

Airflow affects the smallest particles to a greater degree than the larger ones. This makes their travel through the filter more erratic which increases their chances of sticking to fibers.

What About the Particles That Get Through the HEPA Filter?

While some ultrafine particles do pass through the filter, HEPA is not the only line of defense. For example, an air purifier with an activated carbon filter captures most of the remaining particles. It also removes odors.

Placement for Best HEPA Filter Results

Whether you use an air filter at home or work proper placement provides a better chance of removing harmful particles from the air. For starters, placement close to the source of contaminants gets the best results. This could be a room with a litter box, for example. Placing the device between three and five feet off of the ground is also recommended. So is keeping it out of corners and not blocked by furniture or other obstacles. Placement away from direct airflow improves performance. The device should be kept away from moisture as well.

Get an Air Purifiers with HEPA Filter Today

We hope this answers your questions about what is HEPA and how it impacts indoor air quality. To learn more about residential or commercial air cleaning technology or to order an air purifier, give us a call at 727-572-4550.