ASHRAE Journal - February 2021 - 9
LETTERS
clean cabin but not prevent transmission by fomites. But
aircraft cabins are not cleanrooms, and infectious aerosols emitted by an infected person travel in the air many
rows as well as laterally.1,2 Further, airborne infection
risks are not small.3,4 A recent review consistently found
that humans produce pathogens predominately as aerosols or small respirable particles (<5 microns), with PCR
studies identifying infectious aerosols in the air of rooms
with persons ill with COVID-19, the common cold, influenza A and B, tuberculosis, measles, herpes and chicken
pox.5 Low humidity exacerbates the risk.6
Many " authorities " saying high air change rate is the
criteria for good air quality as far as airborne aerosol infections are concerned does not make it true.
Infectious aerosols originate with infected persons creating and shedding virus-not with visible and hidden
building or aircraft cabin materials creating and shedding virus, not with equipment creating and shedding
virus and not with the frost and moisture behind the
insulation creating and shedding virus. Given that fact,
the rate of infectious virion-free air supply to each person, including each ill person and the persons around
them, governs virion concentration in the air around the
ill persons-not air change rate.
While high air change rates provide some protection,
they also result in the virions in the air being inhaled by
others being fresher and more virulent, with less settling
having occurred and the concentrations higher than
in low air change settings. High air change rates can be
the antithesis of low infectious aerosol exposure when
they are the result of tightly packed together persons
in spaces with low ceilings-the situation with aircraft
passenger cabins, for example. The total virion-free air
being supplied is large, but the amount per person is
not. Speaking of low ceilings, spaces with high ceilings
are naturally safer, because body heat and warm breath
rise to the ceiling, taking with them human-generated
aerosols, and stay there if they are not pushed back
down by ceiling fans and the like.
Equation 2, then, in my paper predicts the total number of virion aerosols inhaled by persons in the same
space but not their dispersion or individual inhalation.
It does this prediction by accounting for the per occupant
outdoor air supply rate and filtration rate of particles from
the recirculation air supply. It will also accommodate an
estimation of the filtration benefit of mask wearing on
aerosol exposure reduction, which should eliminate viral
TABLE 1 Narrow body and wide body passenger aircraft influenza A virions inhaled
and infections per ill person, I = 9 L/min·p, t = 5 h, N = 76,000 v/h, HID50 =
900 v. Narrow body: OD = 1 m3 /p, V = 9.4 L/s·p, Ve = 0.65. Wide body: OD =
1.6 m3 /p, V = 11.8 L/s·p, Ve = 1.
NARROW
BODY VIRIONS
INHALED
NARROW BODY
PREDICTED
INFECTIONS
WIDE BODY
VIRIONS
INHALED
WIDE BODY
PREDICTED
INFECTIONS
No Mask
9,244
≤5
4,794
≤3
Mask 50%
2,311
≤1
1,199
≤1
infection risks from surfaces contaminated with fomites
(except for eye touching) and greatly reduce risk from
airborne droplets, both emitted and inhaled. Eye exposure might be important only in hospital-related viral
transmission during ophthalmic practice.3 Mask wearing
will not reduce the infection risks completely, as a justcompleted case study indicates. That study identified a
9.8% to 17.8% COVID-19 attack rate on persons spread
throughout the cabin, some wearing masks, during a 17%
full, seven-hour international flight to Ireland.7
I will assume in the calculations that follow regarding
the August 3 flight from Delhi to Hong Kong that masks
remove 50% of the virions from both our exhaled and
inhaled air. In place of COVID-19 for which there are no
shedding and infectiousness criteria, I will use influenza
A (virions are similar in size to those of COVID-19),3
virion (v) shedding rate and its lowest infectiousness
criteria, which seems appropriate for aircraft due to the
very dry conditions being more favorable to airborne
infection spread due to impairment of nasal mucociliary clearance, innate antiviral defense and tissue repair
function. Table 1 here shows Equation 2 predictions and
all parameters used.
So if influenza A is a valid surrogate and everyone was
wearing masks, it is possible that five COVID-19 infections occurred during that flight from exposure to six
persons with false-negative preflight tests if they were
all shedding.8 It is also possible that if masks were being
worn, no COVID-19 infections occurred during the flight
or, if there were infections, that these persons had not
yet begun shedding at the time of the post-flight tests.
To these predictions must be added any virions inhaled
prior to the flight and those of the 24,000 v/h coarse
(>5 microns) particles shed by ill persons that were aerosolized and inhaled before settling or exiting the cabin.
References
1. Bennett, J.S., B.W. Jones, M.H. Hosni, Y. Zhang, et al. 2013.
FEBRUARY 2021
ashrae.org
ASHRAE JOURNAL
9
http://ashrae.org
ASHRAE Journal - February 2021
Table of Contents for the Digital Edition of ASHRAE Journal - February 2021
Contents
ASHRAE Journal - February 2021 - Intro
ASHRAE Journal - February 2021 - Cover1
ASHRAE Journal - February 2021 - Cover2
ASHRAE Journal - February 2021 - 1
ASHRAE Journal - February 2021 - Contents
ASHRAE Journal - February 2021 - 3
ASHRAE Journal - February 2021 - 4
ASHRAE Journal - February 2021 - 5
ASHRAE Journal - February 2021 - 6
ASHRAE Journal - February 2021 - 7
ASHRAE Journal - February 2021 - 8
ASHRAE Journal - February 2021 - 9
ASHRAE Journal - February 2021 - 10
ASHRAE Journal - February 2021 - 11
ASHRAE Journal - February 2021 - 12
ASHRAE Journal - February 2021 - 13
ASHRAE Journal - February 2021 - 14
ASHRAE Journal - February 2021 - 15
ASHRAE Journal - February 2021 - 16
ASHRAE Journal - February 2021 - 17
ASHRAE Journal - February 2021 - 18
ASHRAE Journal - February 2021 - 19
ASHRAE Journal - February 2021 - 20
ASHRAE Journal - February 2021 - 21
ASHRAE Journal - February 2021 - 22
ASHRAE Journal - February 2021 - 23
ASHRAE Journal - February 2021 - 24
ASHRAE Journal - February 2021 - 25
ASHRAE Journal - February 2021 - 26
ASHRAE Journal - February 2021 - 27
ASHRAE Journal - February 2021 - 28
ASHRAE Journal - February 2021 - 29
ASHRAE Journal - February 2021 - 30
ASHRAE Journal - February 2021 - 31
ASHRAE Journal - February 2021 - 32
ASHRAE Journal - February 2021 - 33
ASHRAE Journal - February 2021 - 34
ASHRAE Journal - February 2021 - 35
ASHRAE Journal - February 2021 - 36
ASHRAE Journal - February 2021 - 37
ASHRAE Journal - February 2021 - 38
ASHRAE Journal - February 2021 - 39
ASHRAE Journal - February 2021 - 40
ASHRAE Journal - February 2021 - 41
ASHRAE Journal - February 2021 - 42
ASHRAE Journal - February 2021 - 43
ASHRAE Journal - February 2021 - 44
ASHRAE Journal - February 2021 - 45
ASHRAE Journal - February 2021 - 46
ASHRAE Journal - February 2021 - 47
ASHRAE Journal - February 2021 - 48
ASHRAE Journal - February 2021 - 49
ASHRAE Journal - February 2021 - 50
ASHRAE Journal - February 2021 - 51
ASHRAE Journal - February 2021 - 52
ASHRAE Journal - February 2021 - 53
ASHRAE Journal - February 2021 - 54
ASHRAE Journal - February 2021 - 55
ASHRAE Journal - February 2021 - 56
ASHRAE Journal - February 2021 - 57
ASHRAE Journal - February 2021 - 58
ASHRAE Journal - February 2021 - 59
ASHRAE Journal - February 2021 - 60
ASHRAE Journal - February 2021 - 61
ASHRAE Journal - February 2021 - 62
ASHRAE Journal - February 2021 - 63
ASHRAE Journal - February 2021 - 64
ASHRAE Journal - February 2021 - 65
ASHRAE Journal - February 2021 - 66
ASHRAE Journal - February 2021 - 67
ASHRAE Journal - February 2021 - 68
ASHRAE Journal - February 2021 - 69
ASHRAE Journal - February 2021 - 70
ASHRAE Journal - February 2021 - 71
ASHRAE Journal - February 2021 - 72
ASHRAE Journal - February 2021 - 73
ASHRAE Journal - February 2021 - 74
ASHRAE Journal - February 2021 - 75
ASHRAE Journal - February 2021 - 76
ASHRAE Journal - February 2021 - 77
ASHRAE Journal - February 2021 - 78
ASHRAE Journal - February 2021 - 79
ASHRAE Journal - February 2021 - 80
ASHRAE Journal - February 2021 - Cover3
ASHRAE Journal - February 2021 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FYONLJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2024november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2024november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_BDMHLG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WJDGRY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ATMAHK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHQRAW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XGMDXI
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_YELQLJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QJLWMC
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