Can COVID-19 Spread in HVAC?

Can COVID-19 Spread Through Your HVAC System? Given primary methods of transmission, it should not be your first thought

By Danny Murtagh, Vice President of Engineering Boston Properties, SF/LA Regions

The general consensus around the spread of COVID-19 is that it is a person-to-person transmitted virus through the droplets released when coughing and sneezing and surface-to-person types of transmission. COVID-19 droplets and aerosols can be spread over longer distances within the conditioned space by air currents and movements. But it’s generally thought not to be a fully airborne virus and not able to travel longer distances through a building’s Heating, Ventilation, Air Conditioning system. HVAC is the term we use in industry to describe the building's mechanical systems assembled to deliver conditioned air to the spaces. The spread of the virus is a back and forth people and surfaces touching and unprotected close contact contamination path.

Droplets from coughing and sneezing landing either from person-to-person or person-to-surfaces-to person have been the main modal methods of transmission of this virus. That being said, the best approach to limiting the spread is according to the WHO (World Health Organization) and CDC (Centers for Disease Control), is through social distancing, good hygiene practices, cleaning and sanitizing as well as face coverings and hand washing and sanitizing frequently. The droplets produced by these actions are not generally considered light or small enough to get carried away longer distances through the HVAC system air streams, although they can travel in excess of 20 feet within a room or space from one person to another and carried by the air movements of the HVAC system through a bigger space. That being said, when we think about that for a moment, think about the air movements within the space and not necessarily the air moving through a commercial HVAC system distances and disruptors, as a more likely explanation of how the HVAC may influence the spread of the virus in a space.

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California Buildings News • Q2 2020

Modes of Transmission

There is a lot of conversation regarding how far smaller particulates can travel suspended in the air, and that the air movement of the HVAC system can further the movement of small droplets, nuclei and aerosols within a space. Nevertheless, the concern about the HVAC system is present and a material perception of concern, so we need to pay attention to it. To that end, what can be done is to assure the HVAC system is in good repair and serviced to provide assurance that the air being circulated in your building is properly conditioned and treated to deliver the best outcomes.

On a commercial level where HVAC systems have many more components and are spread out much farther as depicted below, the HVAC air filters are more substantial than at home, changing filters on a quarterly frequency for pre-filters and annual frequency for final filters are common. These are larger commercial filters that have higher efficiency and capacity than that of your home furnace filter by comparison which you might change more often because they are smaller and less capable of holding dust and particulates. Smaller HVAC Systems More Risky

At home where air distributions are smaller the environment is much more intimate and the spread or aerosols a more important consideration. It is safe to say that many home heating and HVAC systems are barely maintained if at all. Change the air filter and you are likely doing what most homeowners are doing aside from breakdown servicing when something is not working. In fairness, home systems are designed to be more maintenance free in nature.

Good filter maintenance is key to success and a good filter even more key, but not all home systems have return