Many public and private buildings, considered essential to varying degrees, remain open.
These include financial institutions, food, convenience and drug stores, and of course, hospital and health-care facilities. For those buildings that remain open, a few actions related to HVAC systems are suggested, in case some spread of the virus can be affected:
- Increase outdoor air ventilation (use caution in highly polluted areas); with a lower population in the building, this increases the effective dilution ventilation per person.
- Disable demand-controlled ventilation (DCV).
- Further open minimum outdoor air dampers, as high as 100% of the maximum allowable flow rate, per manufacturer’s recommendation, thus eliminating re-circulation (in the mild weather season, this need not affect thermal comfort or humidity, but clearly becomes more difficult in extreme weather).
- Improve central air filtration to the MERV-131 or the highest compatible with the filter rack, and seal edges of the filter2 to limit bypass.
- Keep systems running longer hours, if possible 24/7, to enhance the two actions above.
- Consider portable room air cleaners with HEPA filters.
- Consider UVGI (ultraviolet germicidal irradiation), protecting occupants from radiation3, particularly in high-risk spaces such as waiting rooms.
Information from the ASHRAE website.
ENDNOTE 1: More effective filters with reasonable pressure drop are available, and some increased pressure drop often results in an acceptably small effect on system performance.
ENDNOTE 2: Consider the filters contaminated, protect personnel changing them, and seal them in plastic bags for disposal.
ENDNOTE 3: There is research that shows UVGI in both the upper-room and in-duct configurations can inactivate some disease-transmitting organisms. Either of these takes time to plan and install. For more information, see the ASHRAE PD previously cited and Chapter 62 Ultraviolet Air and Surface Treatment of 2019 ASHRAE Handbook—HVAC Applications.