Ventilation systems are part of daily life at home, the office, and nearly all commercial stores. Concerns have been raised about the role HVAC systems play in the transmission of airborne viruses.
According to the Centers for Disease Control (CDC), many common viruses are thought to spread from person to person through respiratory droplets that are produced when an infected person coughs, sneezes, talks, sings, etc. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs, which is more likely when people are in close contact with one another (within about 6 feet).
Although numerous articles have been published on commercial building air handling systems, the author is unaware of any reports of space to space virus transmission. That being said, ventilation with outside air and proper filtration are important safeguards for the reduction of said transmission.
Recirculation only systems with no, or very limited, outside air can become a large threat. Some real-world examples of these high-risk environments include:
- Wall-mounted “duct-less” air conditioners often seen in restaurants
- Window air conditioners
- Supplemental fans being used within an enclosed environment
Here are a few suggestions to help safeguard against virus transmission:
Filtration – Know Your MERV Number:
The filters that are specified for typical commercial buildings are a MERV 8, which doesn’t help much for the reduction of viruses. The better option is a MERV 13, a filter rated for virus reduction. Some systems, especially residential ones, can have lower airflow rates with these higher MERV numbers though, so capacity could be reduced using these anti-virus varieties. These filters should be changed frequently, with 90 days of service being the maximum period before replacement.
Amp up Your Air Cleaning Technology:
Healthcare facilities, health clubs, airports, and offices can also help stop the spread of viruses by using added protection within their HVAC systems including:
- Ultraviolet C (UV-C) lighting systems – UVC exposure eliminates microbial organisms such as bacteria and viruses by altering the structure and the molecular bonds of their DNA.
- Bipolar ionization systems – Bipolar ionization technology releases charged atoms that attach to and deactivate harmful substances like bacteria, mold, allergens, and viruses.
Specific engineering design is required for the proper use of these technologies.
ASHRAE’s Occupancy Guides can also be referenced to deal with functioning buildings. Further ASHRAE commercial building guidance indicates that periodic flushing of ventilation systems with outside air during off-hours, when occupants leave the space, should be a new ventilation strategy.
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