ASHRAE Journal - January 2021 - 91

Improving Indoor Air Quality
While the primary method of COVID-19 transmission is in droplet
form-from person-to-person or via surfaces-there is a growing body
of scientiﬁc evidence that conﬁrms the virus is also airborne. According
ASHRAE, " Transmission of SARS-CoV-2 through the air is sufficiently
likely that airborne exposure to the virus should be controlled. " As such,
indoor air quality (IAQ) is of critical importance to reducing the spread of
COVID-19 and should be a key consideration in any plans for shared indoor
spaces moving forward. Knowing where to start may be difficult for those
tasked with responsibility for the well-being of others. AHRI's ﬁve steps for
safer schools and workplaces offer practical solutions for improving IAQ.

Find a Qualiﬁed Contractor

A well-designed, modern HVAC
system, properly installed and maintained,
will ensure comfort and productivity while
enhancing health and safety. According to
ASHRAE, building officials should consider
retaining the services of a qualiﬁed design
professional, a certiﬁed commissioning provider (CxP), or a certiﬁed testing,
adjusting and balancing (TAB) service provider, especially for larger, more complex
HVAC systems, such as those found in
schools, large workplaces, or for systems
serving critical spaces within buildings.
Building managers should seek qualiﬁed
contractors that employ technicians
certiﬁed by North American Technician
Excellence.

Ensure Proper Ventilation

In its Interim Guidance for Businesses and Employers, The Centers for Disease
Control and Prevention (CDC) recommends increasing the circulation of outdoor air by opening windows and doors,
and using fans as often as possible. While
it might seem counterintuitive to facilitate
the ﬂow of air that could be moving viral
particles around, these actions help to
disperse pathogens and should be practiced, except if doing so poses a safety or
health risk for occupants.

While MERV 13 and greater ﬁlters are
better at removing particles in the 0.3
micron to 1 micron diameter size (the size
of many virus particles), higher efficiency
ﬁlters require greater air pressures to drive
or force air through the ﬁlter. As such, care
must be taken when increasing the ﬁlter
efficiency in an HVAC system to verify that
the capacity of the system is sufficient to
accommodate the better ﬁlters without
adversely affecting its ability to maintain
the building's required indoor temperature
and humidity conditions. ASHRAE provides guidance for building engineers in
this regard on its COVID-19 Preparedness
Resources website.

Try UV Treatment

It is widely known that ultraviolet
(UV) light treatment can complement
ﬁltration by inactivating particles that can
slip through ﬁlters in homes and commercial buildings. In an article published by
ACHR News, Chair of ASHRAE's Epidemic
Task Force Dr. Bill Bahnﬂeth noted that,

" Even HEPA ﬁlters that have been tested in
the laboratory with viruses will have some
level of penetration...not much-a few
percent. But if anything gets through and
if it's a very virulent pathogen, that means
you're not perfectly protected against
infection by that ﬁlter. " Hence the use of
UV treatment, which is promoted by the
National Institute for Occupational Safety
and Health. In a 2002 study, Effect of
Germicidal Ultraviolet Light (GUV) Installed
in the HVAC Systems on Environmental
Conditions and Workers Health and Well
Being, it is reported that GUV was safe and
" effective in reducing ventilation system
surface microbial contamination as well as
endotoxin, and associated with signiﬁcant
reduction in respirator, mucosal and overall symptoms. "

Control Humidity

Viruses are least viable in buildings
with humidity between 40- and 60-percent. Schools in cooler climates are
susceptible to humidity levels lower than
optimal, making humidiﬁers a necessity.

Next Steps
Schools and workplaces should prioritize building assessment, through which
qualiﬁed technicians conduct tests to
determine appropriate IAQ requirements.
A properly installed, properly maintained
system, with adequate ventilation using
outside air, proper ﬁltration, GUV installation, and appropriate humidity control-go
a long way toward mitigating potential
viral spread. While there may be increased
energy use, it is important to prioritize human health, safety, comfort, and productivity as we move forward.

Improve Filters

Minimum Efficiency Reporting Value
(MERV) is the term used to describe
mechanical ﬁlter efficiency. The higher the
MERV, the better the ability of a ﬁlter to remove particles from the air. ASHRAE recommends that mechanical ﬁlter efficiency
be at least MERV 13 and preferably MERV 14
or better to help mitigate the transmission
of infectious aerosols. Many existing HVAC
systems were designed and installed to
operate using MERV 6 to MERV 8 ﬁlters.

To learn more, visit ahrinet.org/IAQ.

http://www.ahrinet.org/IAQ

ASHRAE Journal - January 2021

Table of Contents for the Digital Edition of ASHRAE Journal - January 2021