ASHRAE Journal - October 2021 - 28

TECHNICAL FEATURE
Central HVAC Filtration vs. Portable Air Purifi er Filtration
Mitigating COVID-19
In Public Spaces
BY ZHIQIANG (JOHN) ZHAI, PH.D., FELLOW ASHRAE; ROBERT BAHL; KEITH TRACE; BHAVESH GUPTA; HE LI, PH.D.
What can the hospitality industry do to reduce the risk of transmission of COVID-19?
Part is recognizing that HVAC systems play a role in mitigating the risk of airborne
transmission of COVID-19.1 At the beginning of the pandemic, hospitality facilities,
including hotels and restaurants, quickly aligned with guidance from the CDC,2,3
WHO4 and other credible organizations such as ASHRAE5,6 by adjusting operating
guidelines to increase outdoor air dilution and improve fi ltration, where possible,
while maintaining guest and associate comfort. This article discusses a comprehensive
study recently conducted by the authors to investigate the effi cacy of portable air
purifi ers to improve air quality in public spaces.
Improving fi ltration can be accomplished by using
fi lters with higher MERV ratings. For instance, higheffi
ciency particulate air (HEPA) fi lters are effective
in removing " 99.97% or better for all particle sizes. " 7
However, fi lters with higher ratings may increase the
pressure drop, which may make them impractical for
some applications. And, even the most effi cient fi lters
in a centralized HVAC system potentially do not mitigate
heavier droplets or other particles that do not get
entrained into the return air vents and may fl oat around
a given space.
Increasing the amount of outdoor air the system
delivers can further dilute particle concentration and
transmission risks. However, outdoor conditions such
as temperature, humidity and air quality can limit the
amount of outdoor air that can be introduced while
maintaining occupant comfort levels.
Building codes and regulations outline the requirements
for ventilation, and hotel heating and air-conditioning
systems are designed to meet these standards.
However, they were not designed to increase this signifi
cantly. Also, hotel guest room heating and air conditioning
systems should be designed with slight positive
pressure, so air does not pass from one room to another.
Another way to increase the ventilation is by leveraging
air purifi ers to provide equivalent air exchanges
Zhiqiang (John) Zhai, Ph.D., is a professor at the University of Colorado at Boulder in Boulder, Colo. He is a member of ASHRAE TC 4.10, Indoor Environmental Modeling. Robert
Bahl is Global Vice President of Engineering & Facilities, and Keith Trace is Senior Director of Engineering & Facilities at Marriott International, Inc. Bhavesh Gupta is Director of
Engineering, Healthy Buildings and INNCOM for Honeywell International. He Li, Ph.D., is a lecturer at the University of Shanghai for Science and Technology, China.
This peer-reviewed article does not represent offi cial ASHRAE guidance. For more information on ASHRAE resources on COVID-19, visit ashrae.org/COVID19.
28
ASHRAE JOURNAL ashrae.o rg O CTO B E R 2 0 2 1
http://www.ashrae.org/COVID19 http://ashrae.org

ASHRAE Journal - October 2021

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

Contents
ASHRAE Journal - October 2021 - Intro
ASHRAE Journal - October 2021 - Cover1
ASHRAE Journal - October 2021 - Cover2
ASHRAE Journal - October 2021 - 1
ASHRAE Journal - October 2021 - Contents
ASHRAE Journal - October 2021 - 3
ASHRAE Journal - October 2021 - 4
ASHRAE Journal - October 2021 - 5
ASHRAE Journal - October 2021 - 6
ASHRAE Journal - October 2021 - 7
ASHRAE Journal - October 2021 - 8
ASHRAE Journal - October 2021 - 9
ASHRAE Journal - October 2021 - 10
ASHRAE Journal - October 2021 - 11
ASHRAE Journal - October 2021 - 12
ASHRAE Journal - October 2021 - 13
ASHRAE Journal - October 2021 - 14
ASHRAE Journal - October 2021 - 15
ASHRAE Journal - October 2021 - 16
ASHRAE Journal - October 2021 - 17
ASHRAE Journal - October 2021 - 18
ASHRAE Journal - October 2021 - 19
ASHRAE Journal - October 2021 - 20
ASHRAE Journal - October 2021 - 21
ASHRAE Journal - October 2021 - 22
ASHRAE Journal - October 2021 - 23
ASHRAE Journal - October 2021 - 24
ASHRAE Journal - October 2021 - 25
ASHRAE Journal - October 2021 - 26
ASHRAE Journal - October 2021 - 27
ASHRAE Journal - October 2021 - 28
ASHRAE Journal - October 2021 - 29
ASHRAE Journal - October 2021 - 30
ASHRAE Journal - October 2021 - 31
ASHRAE Journal - October 2021 - 32
ASHRAE Journal - October 2021 - 33
ASHRAE Journal - October 2021 - 34
ASHRAE Journal - October 2021 - 35
ASHRAE Journal - October 2021 - 36
ASHRAE Journal - October 2021 - 37
ASHRAE Journal - October 2021 - 38
ASHRAE Journal - October 2021 - 39
ASHRAE Journal - October 2021 - 40
ASHRAE Journal - October 2021 - 41
ASHRAE Journal - October 2021 - 42
ASHRAE Journal - October 2021 - 43
ASHRAE Journal - October 2021 - 44
ASHRAE Journal - October 2021 - 45
ASHRAE Journal - October 2021 - 46
ASHRAE Journal - October 2021 - 47
ASHRAE Journal - October 2021 - 48
ASHRAE Journal - October 2021 - 49
ASHRAE Journal - October 2021 - 50
ASHRAE Journal - October 2021 - 51
ASHRAE Journal - October 2021 - 52
ASHRAE Journal - October 2021 - 53
ASHRAE Journal - October 2021 - 54
ASHRAE Journal - October 2021 - 55
ASHRAE Journal - October 2021 - 56
ASHRAE Journal - October 2021 - 57
ASHRAE Journal - October 2021 - 58
ASHRAE Journal - October 2021 - 59
ASHRAE Journal - October 2021 - 60
ASHRAE Journal - October 2021 - 61
ASHRAE Journal - October 2021 - 62
ASHRAE Journal - October 2021 - 63
ASHRAE Journal - October 2021 - 64
ASHRAE Journal - October 2021 - 65
ASHRAE Journal - October 2021 - 66
ASHRAE Journal - October 2021 - 67
ASHRAE Journal - October 2021 - 68
ASHRAE Journal - October 2021 - 69
ASHRAE Journal - October 2021 - 70
ASHRAE Journal - October 2021 - 71
ASHRAE Journal - October 2021 - 72
ASHRAE Journal - October 2021 - HR1
ASHRAE Journal - October 2021 - HR2
ASHRAE Journal - October 2021 - HR3
ASHRAE Journal - October 2021 - HR4
ASHRAE Journal - October 2021 - HR5
ASHRAE Journal - October 2021 - HR6
ASHRAE Journal - October 2021 - HR7
ASHRAE Journal - October 2021 - HR8
ASHRAE Journal - October 2021 - HR9
ASHRAE Journal - October 2021 - HR10
ASHRAE Journal - October 2021 - HR11
ASHRAE Journal - October 2021 - HR12
ASHRAE Journal - October 2021 - HR13
ASHRAE Journal - October 2021 - HR14
ASHRAE Journal - October 2021 - HR15
ASHRAE Journal - October 2021 - HR16
ASHRAE Journal - October 2021 - HR17
ASHRAE Journal - October 2021 - HR18
ASHRAE Journal - October 2021 - HR19
ASHRAE Journal - October 2021 - HR20
ASHRAE Journal - October 2021 - HR21
ASHRAE Journal - October 2021 - HR22
ASHRAE Journal - October 2021 - HR23
ASHRAE Journal - October 2021 - HR24
ASHRAE Journal - October 2021 - 73
ASHRAE Journal - October 2021 - 74
ASHRAE Journal - October 2021 - 75
ASHRAE Journal - October 2021 - 76
ASHRAE Journal - October 2021 - 77
ASHRAE Journal - October 2021 - 78
ASHRAE Journal - October 2021 - 79
ASHRAE Journal - October 2021 - 80
ASHRAE Journal - October 2021 - 81
ASHRAE Journal - October 2021 - 82
ASHRAE Journal - October 2021 - 83
ASHRAE Journal - October 2021 - 84
ASHRAE Journal - October 2021 - 85
ASHRAE Journal - October 2021 - 86
ASHRAE Journal - October 2021 - 87
ASHRAE Journal - October 2021 - 88
ASHRAE Journal - October 2021 - 89
ASHRAE Journal - October 2021 - 90
ASHRAE Journal - October 2021 - 91
ASHRAE Journal - October 2021 - 92
ASHRAE Journal - October 2021 - 93
ASHRAE Journal - October 2021 - 94
ASHRAE Journal - October 2021 - 95
ASHRAE Journal - October 2021 - 96
ASHRAE Journal - October 2021 - Cover3
ASHRAE Journal - October 2021 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IGHYER
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PDRKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XCODFR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QSLFGO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ILKVNM
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2021
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPDJKD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VJKSRY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDHUTC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JPPKRR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDLTTH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CKLLES
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SLDOX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_HJETUK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OLUHGE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ZERDGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QVMNEO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTPOKE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_BBATRE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_STUBMW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TPEMPE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JNMKDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FBTTPA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WQMMNE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TVBRYN
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2020
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_KTUZMA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ABEDGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201910
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201909
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019septmeber_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019september
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201908
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201907
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201906
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201905
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201904
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019april
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201903
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019march
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201902
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201901
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2019
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018december
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018october
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2018
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201810
https://www.nxtbook.com/nxtbooks/ashrae/ashraeinsights_201806
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201805
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201804
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201803
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201712
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201711
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201710
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201709
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201705
https://www.nxtbook.com/nxtbooks/ashrae/ashrae_meetinginsert_201610
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acrexindia
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer
https://www.nxtbook.com/nxtbooks/amca/2014summer2
https://www.nxtbook.com/nxtbooks/amca/2014summer
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acma_2014summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201311
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201309
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acmasupp_2013fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201305
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201303
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2013winter
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201211
https://www.nxtbook.com/nxtbooks/ashrae/achr_expo_mexico2012
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201209
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v3
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201205
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201203
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012winter
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201111_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201109_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2011summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201105
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201103
https://www.nxtbookmedia.com