ASHRAE Journal - May 2021 - 10

TECHNICAL FEATURE

COVID-19

Minimizing Transmission
In High Occupant
Density Settings, Part 1
BY DAVID ROTHAMER, PH.D.; SCOTT SANDERS, PH.D.; DOUGLAS REINDL, PH.D., P.E., FELLOW ASHRAE; TIMOTHY BERTRAM, PH.D.

As the global community learns more about SARS-CoV-2, it seems increasingly probable that a signiﬁcant mode of transmission is via airborne route. In this ﬁrst article
in a two-part series, we review the current base of knowledge regarding transmission
of COVID-19. After brieﬂy introducing a modiﬁed form of the Wells-Riley model for
predicting the conditional probability of infection within indoor environments, we
move on to ﬁeld experiments conducted in an actual classroom to validate the wellmixed assumption for the Wells-Riley model. Finally, we measure effective ﬁltration
efﬁciency for a range of mask types.
The second part of the article (in the June issue of
ASHRAE Journal) applies the Wells-Riley model to these
experimental results to predict the conditional probability of infection for various protective measures.
Since the report of the ﬁrst positive case of COVID-19
in November 2019 in Wuhan, China,1 much has been
learned about the virus and its effect on humans, yet
many questions remain unanswered, including infection control best practices to interrupt or prevent its
transmission to mitigate its effects on both people and
the global economy. To date, the U.S. Food and Drug
Administration has authorized three COVID-19 vaccines

for emergency use,2 and by the end of March 2020,
more than 54 million people in the U.S. have been fully
vaccinated.3 With recent trends in vaccination administration of 2 million doses per day, it will be months
before the majority of the U.S. population could be fully
vaccinated. Beyond COVID-19, it is highly probable that
other, similarly airborne infectious diseases will lead to
future pandemics; what we learn from COVID-19 may
help us decrease their impact.
Foundational to infection control and prevention
is a clear understanding of the mode of transmission
of the pathogen. Early in the COVID-19 pandemic,

David Rothamer, Ph.D., is the Robert Lorenz Professor of mechanical engineering, Scott Sanders, Ph.D., is a professor of mechanical engineering, Douglas Reindl, Ph.D., P.E., is a
professor of mechanical engineering, and Timothy Bertram, Ph.D., is professor of chemistry at the University of Wisconsin, Madison, Wis.
This peer-reviewed article does not represent ofﬁcial ASHRAE guidance. For more information on ASHRAE resources on COVID-19, visit ashrae.org/COVID19.
10

ASHRAE JOURNAL

ashrae.org

M AY 2021

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

ASHRAE Journal - May 2021

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

Contents
ASHRAE Journal - May 2021 - Intro
ASHRAE Journal - May 2021 - Cover1
ASHRAE Journal - May 2021 - Cover2
ASHRAE Journal - May 2021 - 1
ASHRAE Journal - May 2021 - Contents
ASHRAE Journal - May 2021 - 3
ASHRAE Journal - May 2021 - 4
ASHRAE Journal - May 2021 - 5
ASHRAE Journal - May 2021 - 6
ASHRAE Journal - May 2021 - 7
ASHRAE Journal - May 2021 - 8
ASHRAE Journal - May 2021 - 9
ASHRAE Journal - May 2021 - 10
ASHRAE Journal - May 2021 - 11
ASHRAE Journal - May 2021 - 12
ASHRAE Journal - May 2021 - 13
ASHRAE Journal - May 2021 - 14
ASHRAE Journal - May 2021 - 15
ASHRAE Journal - May 2021 - 16
ASHRAE Journal - May 2021 - 17
ASHRAE Journal - May 2021 - 18
ASHRAE Journal - May 2021 - 19
ASHRAE Journal - May 2021 - 20
ASHRAE Journal - May 2021 - 21
ASHRAE Journal - May 2021 - 22
ASHRAE Journal - May 2021 - 23
ASHRAE Journal - May 2021 - 24
ASHRAE Journal - May 2021 - 25
ASHRAE Journal - May 2021 - 26
ASHRAE Journal - May 2021 - 27
ASHRAE Journal - May 2021 - 28
ASHRAE Journal - May 2021 - 29
ASHRAE Journal - May 2021 - 30
ASHRAE Journal - May 2021 - 31
ASHRAE Journal - May 2021 - 32
ASHRAE Journal - May 2021 - 33
ASHRAE Journal - May 2021 - 34
ASHRAE Journal - May 2021 - 35
ASHRAE Journal - May 2021 - 36
ASHRAE Journal - May 2021 - 37
ASHRAE Journal - May 2021 - 38
ASHRAE Journal - May 2021 - 39
ASHRAE Journal - May 2021 - 40
ASHRAE Journal - May 2021 - 41
ASHRAE Journal - May 2021 - 42
ASHRAE Journal - May 2021 - 43
ASHRAE Journal - May 2021 - 44
ASHRAE Journal - May 2021 - 45
ASHRAE Journal - May 2021 - 46
ASHRAE Journal - May 2021 - 47
ASHRAE Journal - May 2021 - 48
ASHRAE Journal - May 2021 - 49
ASHRAE Journal - May 2021 - 50
ASHRAE Journal - May 2021 - 51
ASHRAE Journal - May 2021 - 52
ASHRAE Journal - May 2021 - 53
ASHRAE Journal - May 2021 - 54
ASHRAE Journal - May 2021 - 55
ASHRAE Journal - May 2021 - 56
ASHRAE Journal - May 2021 - 57
ASHRAE Journal - May 2021 - 58
ASHRAE Journal - May 2021 - 59
ASHRAE Journal - May 2021 - 60
ASHRAE Journal - May 2021 - 61
ASHRAE Journal - May 2021 - 62
ASHRAE Journal - May 2021 - 63
ASHRAE Journal - May 2021 - 64
ASHRAE Journal - May 2021 - 65
ASHRAE Journal - May 2021 - 66
ASHRAE Journal - May 2021 - 67
ASHRAE Journal - May 2021 - 68
ASHRAE Journal - May 2021 - 69
ASHRAE Journal - May 2021 - 70
ASHRAE Journal - May 2021 - 71
ASHRAE Journal - May 2021 - 72
ASHRAE Journal - May 2021 - Cover3
ASHRAE Journal - May 2021 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_MCDEBX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WNYSQY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XATVOD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FJSHSS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CCBZDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XDEFVG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHGNBL
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WPKBNJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_UUVCDE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTGDEW
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2023
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LKRFXS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AZSOFG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ERCDBH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QWDFRV
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JHGVDF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPUYHG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SREIBM
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LRTGLK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OKRFGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TZSERA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LVRUIX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RPTVYZ
https://www.nxtbook.com/nxtbooks/ashrae/mini_pub_catalog
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XIYTGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2022
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RFGDOB
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PABXNU
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_REMKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PICVBT
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AOYTVW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JQOPLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IOYTBC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SGAJJF
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