ASHRAE Journal - December 2020 - 38

TECHNICAL FEATURE

Effect of Ventilation
And Filtration on Viral
Infection in Residences
BY HOY BOHANON, P.E, BEAP, LIFE MEMBER ASHRAE; MARWA ZAATARI, PH.D., ASSOCIATE MEMBER ASHRAE

What should people do in their homes regarding HVAC system operation during a
pandemic? According to the CDC, " COVID-19 is thought to spread mainly through
close contact from person-to-person. Some people without symptoms may be able
to spread the virus. We are still learning about how the virus spreads and the severity of illness it causes. " 1 The SARS-CoV-2 virus is transmitted via airborne routes2
and has been detected in HVAC systems.3 The risks of airborne infection for residential scenarios with an infected person can be quantified for purposes of comparing
alternative HVAC approaches. In this article, an evaluation method is proposed for
comparing actions to take for HVAC systems to decrease the risk of viral infection
within residences using a median single-family U.S. residence with central HVAC.
The basic recommendations from ASHRAE regarding
residential HVAC can be accessed on the ASHRAE website.4 These recommendations should not be construed
to replace the advice of the Centers for Disease Control
and Prevention (CDC), World Health Organization
(WHO) or other health authorities. A calculated relative risk of airborne infection for comparison of the
effectiveness of various ventilation or filtration options
is presented here. Generally, more ventilation and
enhanced filtration are recommended by ASHRAE and

other organizations. What is the range of impact of relatively simple low-cost interventions in a residential setting to decrease the risk of COVID-19?
COVID-19 is caused by the SARS-CoV-2 virus.
According to WHO, the virus can be transmitted
by " contact, droplet, airborne, fomite, fecal-oral,
blood-borne, mother-to-child and animal-to-human
transmission. " 5 HVAC is assumed to have little to no
effect on any transmission mode other than airborne.
People can be infectious without showing symptoms

Hoy Bohanon, P.E., is president of Hoy Bohanon Engineering in Clemmons, N.C. He is a former chair of ASHRAE SSPC 62.1, a member of SSPC 62.2 and past member of the
Environmental Health Committee. Marwa Zaatari, Ph.D., is chief science officer of Dzine Partners, LLC in Austin, Texas. She is a member of the ASHRAE Epidemic Task Force
Commercial team, a voting member of SSPC 62.1, vice chair of TC 2.3 and chair for TRG4 Indoor Air Quality Procedure Development.
This peer-reviewed article does not represent official ASHRAE guidance. For more information on ASHRAE resources on COVID-19, visit ashrae.org/COVID19.
38

ASHRAE JOURNAL

ashrae.org

D ECEM BER 2020



http://www.ashrae.org/COVID19 https://www.ashrae.org/

ASHRAE Journal - December 2020

Table of Contents for the Digital Edition of ASHRAE Journal - December 2020

Contents
ASHRAE Journal - December 2020 - Intro
ASHRAE Journal - December 2020 - CT1
ASHRAE Journal - December 2020 - CT2
ASHRAE Journal - December 2020 - Cover1
ASHRAE Journal - December 2020 - Cover2
ASHRAE Journal - December 2020 - 1
ASHRAE Journal - December 2020 - Contents
ASHRAE Journal - December 2020 - 3
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ASHRAE Journal - December 2020 - Cover3
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