ASHRAE Journal - February 2022 - 31

ROUNDTABLE
Corey Metzger, P.E.,
Member ASHRAE
is that the big risks are indoors,
and especially at home because
of the frequency and duration of
the exposure, i.e., eating meals
and sleeping every day. Based on
what we've seen from the studies,
long daily residential exposure is
a big risk because of the potential
transmission between family
members.
We needed to recommend
interventions that would make
economic and practical sense and
that could be implemented quickly. For reducing time
of exposure, you can't do much because you're going to
be there at least in the morning, evening and all night
long: sleeping, eating, taking care of children and simply
living.
So if you can't reduce duration, then reducing airborne
viral concentration will be the quickest and most
effective short-term risk reduction measure. For that,
opening windows in the home to dilute and remove the
viral cloud is possible in some locations that have moderate
climates. But it is not particularly effective and is
often out of the question in most of the world because of
weather, outdoor pollution or wildfi res or because older
windows sometimes simply won't open. So eventually
we decided that in most cases, portable high effi ciency
particulate air fi lters (HEPAs) are probably the most
immediate and lowest-cost means of reliably reducing
concentration of airborne viruses in a home.
Luke Leung (Commercial): The fi rst thing we learned
quickly is the upgrade of the fi ltration devices is important
because a lot of the commercial buildings are still
hermetically sealed and have MERV 8 fi lters, especially
in the U.S. We are seeing that change-maybe more permanently-regarding
both the discussion of openings to
outdoors and MERV 13 fi lters.
The second piece is we quickly saw the importance of
fl exible density in offi ce buildings, and I think many
of us will experience this kind of fl exible workplace in
the future where the density will be like an accordion
depending on the risk of going to the offi ce.
Third, we quickly learned a lot of the outbreaks are not
inside the offi ce boundary, including the elevator. A lot
of people are concerned about a confi ned environment
of the elevator, but we learned that the air change in new
elevators can be beyond 300 cfm. And you do the math,
it's well beyond 70 air changes per hour, a lot more than
the typical offi ce.
Corey Metzger (Schools): The key thing we learned is
the number of school facilities that don't have ventilation
systems at all or are signifi cantly underventilated.
Probably the most common question we received was
how to handle the number of facilities that didn't have
any ventilation or had only operable windows-what to
do in those spaces.
Certainly we need to look at how to help continue to
push the industry forward in addressing those needs in
schools. I think the biggest areas of need seem to be in
urban districts and rural districts.
From my perspective, the biggest question in the
spaces that otherwise meet our recommendations is how
to best distribute airfl ow. We've got a higher occupant
density in a typical classroom than you're going to have
in an offi ce space or in many other occupancy types.
Thinking about how we move air through the space to
minimize the potential for transmission in the ETF's
Core Recommendations, we're seeking a well-mixed
space but looking at-as we move forward in the future-
if there's a way to do it better to prevent transmission
and understanding what that is.
The last item I would highlight are the steps we took for
in-between spaces that either didn't meet our minimum
recommendations or where there were more signifi cant
concerns-how we identify short-term improvements
like in-room air cleaners and evaluate those and then
get them implemented correctly, described in the aircleaner
document [ " In-Room Air Cleaner Guidance for
Reducing COVID-19 in Air in Your Space/Room " ]. There's
certainly potential to put those in as more or less a placebo.
In many cases, it may not actually have much real
benefi t other than improving folks' comfort.
Jason DeGraw (Transportation): I think we as a team
determined relatively quickly that any effective reduction
in risk is only going to be accomplished holistically
in as varied a situation as transportation . Not only are
buildings involved-airports, bus stations, subway stations,
that sort of thing-there are also the actual vehicles
themselves. You're not going to be able to have an effective
mitigation strategy or reduced risk for people if
you're not attacking the whole problem. The weakest
link is what's going to get you.
F E B R U A RY 2 0 2 2 ashrae.o rg ASHRAE JOURNAL
31
http://ashrae.org
ASHRAE Journal - February 2022

Table of Contents for the Digital Edition of ASHRAE Journal - February 2022
