There are chances that you have been hearing a lot about HEPA AC filters and HVAC filters as a solution for preventing the transmission of COVID-19. Here is what you probably don’t know. There are downsides to using HEPA filters in your HVAC system. In the next sections, you will know some important facts.

What do HEPA AC filters do?

A HEPA (High Efficiency Particulate Air) filter is a very thick and dense filter that is designed to capture tiny particles in the air passing through it, including pollutants and allergens.

The size of the particles is very important. HEPA filters can capture 99.97% of particles as small as 0.3 microns (the average cross section of a human hair is 50 microns) in size. That means HEPA filters do a great job of capturing particles like dust mites (100 – 300 microns), pollen (10 – 1000 microns), and even bacteria (1 – 10 microns). Viruses are more difficult, because they can be much smaller than a HEPA AC filter can capture.

Why a HEPA AC filter may not be a useful as a COVID mitigation solution?

HEPA filters can’t effectively trap all COVID-19 virus particles

The problem is, coronavirus particles can be much smaller than 0.3 microns. Experts say the COVID-19 particles can be as small as 0.06 microns—that’s six-one hundredths of a micron! While larger droplets and larger particles may be trapped by a HEPA filter, small individual particles can still pass through it.

Also, there are other reasons why installing HEPA AC filters is not an appropriate solution for COVID.

Your system probably can’t accommodate a HEPA AC filter

A HEPA AC filter is between 5 inches and 8 inches thick. Light commercial and residential air conditioning systems are designed to use much thinner filters. The filter housing typically can’t hold a 5 to 8 inch HEPA filter. So, you’ll need modifications to your system, if you want to install them that can be expensive (especially for commercial systems with multiple filters).

HVAC HEPA filters can decrease performance and cause breakdowns

Because HEPA filters are so thick, your system’s fan probably won’t have enough horsepower to pull air through the filter. Without that, the internal pressure drop across the filter causes a strain on the system. Decreased airflow means your system can’t cool as well. It will need to run longer to reach set temperature. That uses more electricity, increases wear on parts, and can lead to more serious component failures.

HEPA filters are expensive

HEPA filters can cost several hundred dollars each compared to a standard size MERV 8 filter, which will cost approximately $5.50 each or a MERV 13 filter that will cost approximately $17 each. And because they remove more dust and debris from the air, you’ll need to change them more often.

Alternative COVID mitigation options

Most people know by now, the most effective tactics for preventing the spread of COVID are hand-washing, social distancing, and wearing a mask. However, these additional tactics can help eliminate virus particles that may make their way into your HVAC system.

MERV 13 filters offer some protection, with less expense

‘MERV’ (Minimum Efficiency Reporting Values) is a rating system for HVAC and other filters. The higher the MERV rating value on a filter, the smaller the particle it can capture, and with greater efficiency. Standard HVAC air filters used in most commercial and residential properties are rated at MERV 8. HEPA filters are rated between MERV 17 and MERV 20.

If you are concerned about indoor air quality above and beyond preventing COVID transmission, we recommend MERV 13 filters. This advice is based on recommendations from the CDC and ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers).

MERV 13 filters offer some protection and can capture 50% of particles in the size range of COVID particles. And they can definitely cut down on dust and allergens. More HVAC filter housings can accommodate them (but not all), and they are far less expensive than HEPA filters (although still 3 times the cost of standard MERV 8 filters). There may still be issues to consider with regard to airflow and performance with some HVAC systems, so always consult with HVAC professionals before buying them so that you fully understand the cost and the potential benefit.

One caveat: as you might expect given the circumstances, demand is very high for MERV 13 filters. We are currently experiencing 2 to 3 week lead times and it’s likely to get worse before it gets better.

UV light technology keeps HVAC surfaces clean

You may have heard that ultraviolet (UV) light can deactivate coronavirus particles. UV air purifiers, when installed inside your HVAC system, can help in killing particles (including viruses, bacteria, and mold) that may accumulate on system components. They work particularly well to keep AC evaporator coils clean. That’s helpful because clean coils keep your system running effectively and efficiently, and can decrease the cost of ongoing maintenance.

Unfortunately, UV lights don’t work as well at destroying airborne particles inside an HVAC system. That’s because particles need to remain in the UV light’s ‘kill zone’ long enough to be destroyed. Inside an HVAC system, fans typically are moving the air too quickly to kill airborne contaminants.

Advanced oxidation and ionization technology cleans the air

These types of air purifiers can help in removing airborne virus particles (and other contaminants) within your HVAC system. They are installed in a plenum, which is an air distribution chamber between the structural ceiling and drop ceiling, that’s connected to your ductwork.

The technology takes oxygen molecules from the air and converts them into charged atoms that then cluster around microparticles, surrounding and deactivating harmful substances like airborne mold, bacteria, allergens, and viruses. The larger particles result in more efficient filtering of the air. The process also produces friendly oxidizers found in nature that get distributed throughout your space, not only within your HVAC system. They have also been proven effective at reducing harmful VOCs and odours.

A combination of this technology along with upgraded MERV 13 filters will provide a much improved indoor air environment.

These solutions are not right for every situation, but can be extremely helpful in the right setting. And they can provide peace of mind for business owners who want to do everything they can to protect their employees and customers.

Rohan Kuldhar is from the Project Sales Department of Fusion HVAC Solutions Pvt. Ltd. He possesses a BE Mechanical degree.

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