Adam Gloss revisits his post from March 31 with current information on best practices for reducing the spread of coronavirus via HVAC systems.  

With developments around the coronavirus moving quickly, there is a lot of conflicting information about whether the virus is being found in the air (becoming aerosolized). According to the latest information from the World Health Organization, while this is possible in some rare circumstances, the primary means of transmission remains through droplet and contact transmission, not airborne transmission.

Beyond this, a recent research report from Beihang University in China indicated that higher temperatures and humidity reduced transmission of the virus. This is consistent with general behaviors of viruses and other particulate, which see a reduction in aerosolization when indoor relative humidity is between 30 to 60 percent. (Particles tend not to remain suspended when humidity is higher.)

So what does all of this actually this mean for what you can do to reduce the spread of viruses like the coronavirus?

In general, buildings are designed to have relative humidity (RH) controlled in this healthy range already  to provide good indoor air quality (preventing mold growth, helping control particulates in the air). If you are increasing ventilation and bringing in more outdoor air, it can impact your indoor RH. You should ensure indoor RH remains in a healthy range when adjusting ventilation. We can work with you to make the appropriate adjustments if you are unsure how to do so.

We continue to recommend:

1. Following CDC guidelines for social distancing, enhanced cleaning, hand and respiratory hygiene and isolation in cases of infection or suspected infection.
2. Increasing ventilation as much as possible to dilute and exchange indoor air, while maintaining healthy indoor RH ranges.
3. Using portable HEPA filtration in higher risk areas.
4. Considering UVGI systems if you have significant concerns about airborne transmission
5. Central HEPA filtration can also be considered (if practical to retrofit)

Adam Gloss is the Director and General Manager of Service at McKinstry