ASHRAE Journal - January 2021 - 26

TECHNICAL FEATURE

of outdoor air during high demand seasons.
In many ways the ventilation system acts as the primary engineering control for diluting viral particulates,
helping to reduce overall concentration in a space. You
want to have it effectively deal with the source. However,
zone dampers should not be used to reduce the amount
of air that's being supplied to a space due to lower occupancy, as those lower levels of air circulation may not be
able to effectively dilute particulates within the occupied
zone. See Reference 1 for additional guidance. In those
cases, the judicious use and proper sizing of localized
HEPA filters could be a useful adjunct to increase the
circulation of clean, essentially particle free air and to
increase the localized effective air exchange rate within
those spaces.
While the specifics of the performance checklist may
vary across building types and sizes and the types of
HVAC systems serving them, some general steps exist
that all facilities engineers may want to consider (Table 1).
The length of time needed to perform this work will
vary across building types and sizes and will also depend
on the size of the staff managing it. In general, plan for
two to three weeks of ongoing adjustments if you are
doing it in-house. This gives facilities engineers time to
fine-tune systems, order and install replacement parts
and perform a systematic check of all systems.

TABLE 1 HVAC system inspection.
UNIT

Inspect All Components Within the
Unit, Including Filters and Air Bypass
AIR-HANDLING Heating and Cooling Coils
UNIT Condensate Pans
Condensate Drain Lines
Humidification Systems

HVAC system disinfection may not be necessary to
reduce the spread of SARS-CoV-2, but that doesn't leave
building engineers in the clear. Now is the time to perform any deferred or near-due HVAC maintenance to
ensure this system is working effectively. Keeping building occupants comfortable and safe will come down
to solid equipment maintenance practices and a clear
understanding of how your facility's ventilation systems
are meant to function.
It is also the time to talk with building owners about
how critical HVAC performance is to ensuring a healthy
building. Although dramatic decreases in COVID-19
infections occurred during the spring and summer
of 2020, many areas are seeing another surge as they
enter the cooler seasons of the year25 and the use of
outdoor air for increasing ventilation is being curtailed.
Clearly, safe, effectively functioning buildings will play
a critical role in mitigating ongoing risks. This makes
it more important than ever that facilities managers
26

ASHRAE JOURNAL

ashrae.org

JAN UARY 2021

Acoustic Insulation
Fans and Fan Compartments
Dampers
Energy Recovery Devices
General Unit Integrity

SUPPLY AIR

Air Duct Integrity
Controls

Mixing/Control Boxes
Reheat Coils

RETURN AIR

Dampers
Return Plenums

Grilles

EXHAUST AIR

General Exhaust
Bathroom Exhaust

Heat Recovery Exhaust
(If Present)

See the ASHRAE Epidemic Task Force " Building Readiness "
guide's preoccupancy checklist, preoccupancy building readiness
assessment and school and university HVAC inspection checklist
for additional guidance.

and building engineers become part of the discussion
and decision-making process around keeping interior
spaces safe. Coupling a thorough understanding of the
science behind SARS-CoV-2 and other virus transmission with knowledge of building system performance
makes building professionals' voices a particularly critical part of the conversation around safety today and in
the future.

References
Become Part of the Safety Conversation

TASK

1. ASHRAE Epidemic Task Force. 2020. " Building Readiness. "
ASHRAE. https://tinyurl.com/y5r92ohs
2. ECDC. 2020. " Heating, Ventilation and Air-Conditioning
Systems in the Context of COVID-19. " European Centre for Disease
Prevention and Control.
3. Wells, W.F. 1934. " On air-borne infection-Study II droplets
and droplet nuclei. " Am. J. Hyg. 20(3):611 - 618.
4. Gralton, J., E. Tovey, M.L. McLaws, W.D. Rawlinson.
2011. " The role of particle size in aerosolised pathogen
transmission: a review. " The Journal of infection 62(1):1 - 13.
https://doi.org/10.1016/j.jinf.2010.11.010
5. Morawska, L., J. Cao. 2020. " Airborne transmission of SARSCoV-2: The world should face the reality. " Environment International
139(June):105730.
6. ASHRAE. 2020. " ASHRAE Position Document on Infectious
Aerosols. " ASHRAE. https://tinyurl.com/y8meg96z
7. Riddell, S., S. Goldie, A. Hill, et al. 2020. " The effect of
temperature on persistence of SARS-CoV-2 on common surfaces. "
Virol J 17(145). https://doi.org/10.1186/s12985-020-01418-7
8. Chin, A.W.H., J.T.S. Chu, M.R.A. Perera, K.P.Y
Hui, et al. 2020. " Stability of SARS-CoV-2 in different
environmental conditions. " The Lancet Microbe 1(1):e10.
https://doi.org/10.1016/S2666-5247(20)30003-3
9. CDC. 2020. " Reopening Guidance for Cleaning and
Disinfecting Public Spaces, Workplaces, Businesses, Schools,
and Homes. " Centers for Disease Control and Prevention.

https://www.tinyurl.com/y5r92ohs https://www.doi.org/10.1016/j.jinf.2010.11.010 https://www.tinyurl.com/y8meg96z https://www.doi.org/10.1186/s12985-020-01418-7 https://www.doi.org/10.1016/S2666-5247(20)30003-3 https://www.ashrae.org/

ASHRAE Journal - January 2021

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