During the COVID-19 pandemic, you may have heard that HVAC systems could circulate the virus throughout buildings. Since that information first came to light, some people in the HVAC industry have been touting HEPA filtration as a means of controlling viral circulation indoors. If a filter can take care of tiny viruses, it probably works wonders against pollen and dust. It sounds like a dream come true for home and business owners!

But we’re getting ahead of ourselves. Are the claims even true? Are HEPA filters that much better than regular HVAC filters? Should you consider using HEPA filtration in your home or business?

None of these questions have a simple answer, so we’re going to discuss what HEPA filters are, what they do, and if they are worth your time and money.

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HEPA stands for “high-efficiency particle arrestance.” So, a HEPA filter meets a strict set of performance criteria according to the US Department of Energy (DOE). 

According to the DOE, a filter qualifies as HEPA-quality if it can catch 99.97% of particles sized at 0.3 microns. One micron is one-millionth of a meter (or one-thousandth of a millimeter). An average strand of human hair has a diameter of 50-70 microns.

So, HEPA refers to a performance standard rather than a brand name. However, you may see some filters labeled “True HEPA.” “True HEPA” has no scientific basis whatsoever. Instead, “True HEPA” is a marketing term for filters that may or may NOT meet the US DOE standard.


The answer is a bit complicated. Although the earth is home to several coronaviruses that vary in size, let’s focus on the virus that causes COVID-19 (SARS-CoV-2).

According to a National Center of Biotechnology Information (NCBI) article by Bar-On, Flamholz, Milo, and Phillips, the SARS-CoV-2 virus’s diameter is approximately 0.1 micron. So, that’s too small for the HEPA standard, right?

On paper, the answer is yes. However, in the field, it’s a bit more complicated. HEPA filtration is actually MORE effective on particles smaller than 0.3 microns due to a phenomenon called Brownian motion. 

Brownian motion happens when extremely small particles move erratically due to small changes in the airstream (velocity, pressure, etc.). So, those particles constantly change direction and will have a hard time slipping through the HEPA filter with the airstream. Once those tiny particles collide with the filter media, they remain attached to the fiber and won’t travel with the airstream. We call that type of filtration “diffusion.”

So, even though the facts may seem counterintuitive, HEPA filters ARE effective at catching tiny particles like viruses.


If a HEPA filter can catch particles as small as viruses, it can catch much more than just viruses.

HEPA filters are an excellent solution for catching pollen, pet dander, and other allergens. So, you may consider using HEPA filtration in your business if you deal with lots of allergens. For example, a veterinary office could benefit from HEPA filtration. It is also a good idea to consider using HEPA filtration if your business has lots of plants inside or near the building.

HEPA filtration is also effective against volatile organic compounds (VOCs). VOCs are gases emitted from common household products, such as paints, cleaning products, and air fresheners. Many VOCs have the potential to cause adverse health effects.

So, facilities that use lots of cleaners and disinfectants, such as medical facilities, would benefit from HEPA filtration. Businesses that contain high volumes of hobby/craft supplies, pesticides, and fuel-related products can also be made safer with HEPA filtration. In the image below, a Kalos installation technician is setting up a bypass HEPA filter for a dentist’s office.


While HEPA filters may do a good job of catching harmful substances and boosting indoor air quality, they are restrictive. Running ALL of your indoor air through a HEPA filtration system will be challenging. So, some home and business owners opt for a bypass HEPA filter. A bypass solution only filters a portion of the airflow through the HEPA filter.

Instead of using a HEPA filter, some home and business owners choose to install UV lighting, cool plasma, or oxidizing ions on regular filters to reach that 99.97% effectiveness. 

However, those alternatives have question marks of their own. For example, they may introduce ozone to the building or have costly maintenance. They also aren’t necessarily effective on particles smaller than 0.3 microns.


Ultimately, the choice to use HEPA filtration comes down to you. However, at Kalos, we endorse HEPA filtration solutions and have been offering them to our customers for a little while. 

We acknowledge the challenges of HEPA filters, but we do our best to minimize them as much as possible. When we set up HEPA filtration systems, we test the static pressure to ensure that it remains at acceptable levels. Static pressure is an indicator of airflow and can give us quite a bit of information about your HVAC system’s functioning.

HEPA filtration’s combination of indoor air quality and cost-effectiveness is unparalleled.