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Let’s Clear The Air

We are indoor air quality experts dedicated to helping people open their doors again with confidence, from homes and schools to businesses and medical facilities. Right now, everyone has questions and concerns about the air around them. IndoorAirHygiene.com is where you can find answers and request advice.

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Yes, the COVID-19 illness is caused by the Coronavirus SARS-CoV-2 which according to the Centers for Disease Control (CDC) is thought be transmitted via respiratory droplets from infected persons via the air. Although the majority of these droplets are heavy enough to drop out of the air within 6 feet of the infected person, there is likely a percentage of droplets small enough to remain airborne and circulate through the HVAC system. A properly selected HVAC filter becomes the determining factor on if these pathogens are recirculated back into the air flow of your system.

Yes, several studies have shown that an HVAC system with a properly selected filter can reduce the spread of bacteria and viruses. One of these studies performed in 2013 modeled the spread of the influenza virus in an office environment and showed that HVAC systems with the appropriate filtration can offer a 7X reduction in spread of the virus.1, Although there has not been any significant research completed specifically on SARS-CoV-2 yet, there are studies on similar pathogens which have shown that HVAC systems can impact the spread of virus particles.

1“HVAC filtration for controlling infectious airborne disease transmission in indoor environments: Predicting risk reductions and operational costs”

Yes, with the proper type of filter selected. Virus particles, or virons, can be as small as 0.02 to 0.4 micrometers. This is 150 times smaller than the diameter of a typical human hair. Most typical HVAC air filters are not designed to remove a significant number of these extremely small particles, however there are filters such as HEPA and ULPA filters which remove close to 100% (99.97%+) of these particles when properly installed.

However, most virus particles including the ones that cause COVID-19 rarely, if ever, travel on their own. They are almost always attached to much larger moisture droplets which are expelled from the infected individual. The capture rate of these larger particles is much greater and therefore it can be stated that air filters with higher MERV ratings (13+)2 are effective tools to capture the airborne particulate that carries airborne virus.

2 ASHRAE Position Document on Infectious Aerosols – April 14, 2020

There are several new technologies to consider! Since HVAC systems can impact the spread of virus particulate in several ways, understanding those factors is an important part of infection control protocols. First off, and most importantly, you will want to consider which type and performance rating of air filters you have installed (it is recommended to have at least MERV 13 filters installed)3. This choice will impact both the number and size of particles removed, along with the volume of airflow produced by the unit. Premium filtration formats like V-Bank Mini-Pleats, utilize modern filtration components which allow for higher removal performance without sacrificing airflow.

There are also technologies related to the cleanliness of an HVAC system that should be considered. These include both cleaning chemicals which can disinfect the HVAC system components, along with other devices such as UV-C germicidal lighting which can inhibit the growth of microbes within the unit.

In addition to the particulate air filters, there are technologies such as Filtration Group’s Purafil gas phase filtration modules which utilize chemical and molecular filter media to remove gas and chemical contaminants which are not captured by traditional particulate filtration. This works in conjunction with your standard HVAC system as a second line of defense.

3 ASHRAE Position Document on Infectious Aerosols – April 14, 2020

High MERV rated filters and those that utilize oxidizing media. To reduce the spread of the virus the viron particles need to either be captured or killed. Most HVAC filters will focus on capturing the virus. In this case, the higher the MERV rating, the greater the capture rate of potentially infectious particles. Although most HVAC systems were not engineered for optimum infection control, increasing the efficiency level above MERV 13 is recommended by the US National body who sets guidelines for the HVAC industry.4,5

Filters which utilize chemical filtration to inactivate the virus such as those with Purafil’s Puraward media, may further reduce the spread of the virus by killing the pathogens in addition to just capturing them.

4 ASHRAE Position Document on Infectious Aerosols – April 14, 2020

5 “HVAC filtration for controlling infectious airborne disease transmission in indoor environments: Predicting risk reductions and operational costs

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IndoorAirHygiene.com is a free resource brought to you by the thought leaders within Madison Industries. We are dedicated to sharing knowledge about indoor air quality that can help people breathe easy every day.

Our companies specialize in technologies that help deliver clean air for people around the world. Our products work together to purify the air we breathe by removing pollutants, managing humidity, bringing fresh outside air to indoor spaces and cleaning recirculated indoor air. Because every breath matters.