ASHRAE Journal - May 2020 - 73

COLUMN IEQ APPLICATIONS

* droplets and possibly particles spread between
people in close proximity.
For this reason, basic principles of social distancing (1
to 2 m or 3 to 6.5 ft), surface cleaning and disinfection,
handwashing and other strategies of good hygiene are
far more important than anything related to the HVAC
system.7 In the middle-Atlantic region of the United
States where I work, malls, museums, theaters, gyms
and other places where groups of people gather are
closed and there are "stay at home"8 orders. This is a
"game" of chance, and the fewer individuals who come
in close contact with each other, the lower the probability for spread of the disease. Since symptoms do not
become apparent for days or weeks, each of us must
behave as though we are infected.
Other public buildings, considered essential to varying
degrees, remain open. These include food, hardware
and drug stores, and of course, hospital and health-care
facilities (which are beyond the scope of this article).
Anecdotally, some universities are allowing some or all
faculty, staff and graduate students to conduct essential
research and online classes. Banks and other service
organizations are open to staff and are receiving customers by appointment only, and private and government
workplaces are open with work at home for some or all
encouraged or mandated.
For those buildings that remain open, in addition to
the policies described above, non-HVAC actions include:
* Increase disinfection of frequently touched surfaces.9
* Install more hand sanitation dispensers, assuming
they can be procured.
* Supervise or shut down food preparation and
warming areas, including the ofﬁce pantry and coffee
station.
* Close or post warning signs at water fountains in
favor of bottle ﬁlling stations and sinks, or even better,
encourage employees to bring their water from home.
Once the basics above are covered, 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%, thus eliminating recirculation (in the mild

weather season, this need not affect thermal comfort or
humidity, but clearly becomes more difﬁcult in extreme
weather).
* Improve central10 air ﬁltration to the MERV-1311
or the highest compatible with the ﬁlter rack, and seal
edges of the ﬁlter12 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 radiation,13 particularly in
high-risk spaces such as waiting rooms, prisons and
shelters.
Construction sites present unique challenges. Much,
but not all, construction work has the recommended
social distancing; much, but not all, is outdoors or in
partially enclosed and therefore well-ventilated buildings; and many, but not all, workers already use personal protective equipment such as masks14 and gloves.
Governments in some locations have mandated closure
of construction sites, while in others work proceeds.15
Engineers who perform ﬁeld observations, commissioning or special inspections must consider what work can
be postponed, performed remotely, or conducted using
photographic documentation, and what personal precautions to take when site visitation is unavoidable.
If you, the reader, are called upon to advise building
operators, please use the above general guidance, and be
sure to combine it with knowledge of the speciﬁc HVAC
system type in a building and the purpose and use of
the facility. Like all hazards, risk can be reduced but not
eliminated, so be sure to communicate the limitations
of the HVAC system and our current state of knowledge
about the virus and its spread.
We all have a role to play to control the spread of this
disease. HVAC is part of it and even more signiﬁcant are
social distancing, hygiene and the inﬂuence we can have
on personal behavior.
Thanks to William P. Bahnﬂeth, Ph.D., P.E., Presidential
Member/Fellow ASHRAE, Lew Harriman, Fellow ASHRAE,
Yuguo Li, Ph.D., Fellow ASHRAE, Andrew K. Persily, Ph.D.,
Fellow ASHRAE, and Pawel Wargocki, Ph.D., Member
ASHRAE for their review of preliminary drafts of this
article. Any errors that remain are the author's alone.

Endnotes

1. According to the WHO, COVID-19 is the name given on February
11, 2020 by the ICTV (International Committee on Taxonomy
M AY 2020

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