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Airborne Coronavirus and Your Building's HVAC System

Airborne Coronavirus and Your Building's HVAC System

Amid all of the discussion of mask policies and sanitization, one area often gets overlooked: the HVAC system. Research has shown that the novel coronavirus is much more likely to infect people in a confined, poorly-ventilated space than it is outdoors. What can you do to make sure the air in your facility is clean?

How does SARS-CoV-2 spread?

According to the Centers for Disease Control, the virus responsible for COVID-19 primarily spreads through person-to-person contact. This means that if an infected person coughs, sneezes, talks, or otherwise sheds respiratory droplets, and these droplets get into the eyes, nose, or mouth of an uninfected person, that uninfected person can become infected. There's also reason to believe that an uninfected person may pick up the virus by touching a contaminated surface, then touching their eyes, nose, or mouth. While the CDC hasn't indicated that airborne transmission is a major risk, they acknowledge that one of the most important things that facility managers and employers can do is improve building ventilation. Dr. Fauci has also said that airborne transmission is "something that we can't completely rule out." In mid-July, the World Health Organization updated a scientific brief to say that reports of COVID-19 outbreaks in closed settings, such as bars, churches, and restaurants, indicates that airborne transmission may be possible.

Are HVAC systems responsible for circulating the virus?

A study by the University of Oregon found the SARS-CoV-2 virus present in 25% of the vents in hospital rooms that saw COVID-19 patients, suggesting that indoor ventilation systems can potentially contribute to the spread of the virus. It's not yet fully understood exactly how much of a risk they pose, but one thing is for certain -- poorly-ventilated indoor spaces are correlated with spikes in COVID-19. Even if HVAC systems aren't found to be responsible for circulating the virus themselves, they can still help mitigate the risk of infection.

How can HVAC systems prevent the spread?

Proper filtration is one crucial element of cleaning any potential viral particles from the air. Filters are generally measured in Minimum Efficiency Reporting Values (MERV). The higher the MERV rating, the more efficient the filter. As filter efficiency increases, it requires more energy for the system to force air through it. This is why most commercial systems don't use the highest-rated filters that they possibly can -- they trade energy efficiency for filtration efficiency. If possible, HVAC systems should use a HEPA filter. If not, they should use the highest MERV filter they can handle. UV lighting units can also help sanitize air. These can be installed in the ventilation system itself, treating the air as it passes through. New advances in specific UV wavelengths show some very promising results when it comes to inactivating the novel coronavirus. Humidity control is another important factor. Maintaining a level of 40-60% humidity can help decrease the risk of infection for the building's occupants.

Are there new technologies that can help HVAC systems keep the air cleaner?

New UV sterilization systems that employ UV-C can help limit the spread of the novel coronavirus. While germicidal UV units have been in use for a long time, interest in UV-C is relatively new. UV-C is one of the types of ultraviolet light that the sun gives off, but gets filtered out by the ozone layer before it can reach the Earth. It's a good thing, too -- in addition to inactivating viruses, it can also cause serious harm to living cells. This is what makes it perfect for use in an HVAC unit. It can sanitize the air, without coming into contact with any occupants.

How are some employers and facility managers handling the situation?

In many cases, they're trading sustainability for employee health. Not only are they switching to filters with a higher MERV rating, but they're also increasing the number of times indoor spaces get "flushed" with outdoor air. If flushing isn't an option, increasing the air change rate can still help. Some are also creating more separation within buildings, by isolating areas and setting up smaller HVAC units. This keeps air from mixing as easily, so, if there's an outbreak, it is easier to confine to one area. In old buildings without central HVAC units, facility managers are bringing in fans and opening windows to bring in as much outdoor air as possible. When it comes to protecting employees and guests from SARS-CoV-2, improving ventilation is key. Even though we don't yet fully understand all of the ways it's possible to transmit the novel coronavirus, data shows that crowded, poorly-ventilated areas quickly turn into hotbeds. By increasing the air change rate, bringing in as much outdoor air as possible, controlling humidity, isolating areas, and installing UV units and better filters, facility managers can help keep the air as virus-free as possible.

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