ASHRAE Journal - September 2021 - 39

TECHNICAL FEATURE
FIGURE 1 Clean air delivery rate equation.2
CADR=−
Vk ktn
()
FIGURE 2 Indoor concentration of particles formula.6
Ct
() =
kn = Natural decay constant rate (no air cleaner in the
test chamber)
kt = Test decay constant
V = Volume of test chamber (ft3)
CADR = Clean air delivery rate (cfm)
k decay constant is calculated by:
C Ce
ti =
to
Cti = Concentration at time ti (particles/cc)
k = Decay constant
Cto = Concentration at t =0 (initial)
ti
= Time at t = I (minutes)
with a base case condition of 2 ach of outdoor air, the
study showed that droplet nuclei concentrations could
be reduced between 30% to 90% by adding in-room
fi ltration.
Other results showed that HEPA fi lter media and 90%
effi cient fi lter media performed the same in their test.
Since the droplet nuclei emitted into the room were
unconfi ned, the single-pass effi ciency had less bearing
on the results because the droplet nuclei could bypass
the fi lter to enter the breathing zone of a susceptible
person. If the source to receptor path can be disrupted,
greater protection can be obtained. The results also
showed that increasing the eACH rates sometime
increased effi ciency and other times decreased the effi -
ciency. This effect could be due to the increased eACH
affecting the airfl ow patterns in the room.6
A simulation by Qian, et al., of portable HEPA air cleaners
found that the " strong supply air from the portable
HEPA fi lter interacted with the room airfl ow pattern
and became dominant , introducing global airfl ow mixing
in the room. " 7 The impact of the in-room fi ltration
unit should be taken into account when evaluating a
room's air distribution design. An equation for the rate
of change of the indoor airborne concentration can be
used to evaluate the relationship between ventilation
and fi ltration. Figure 2 shows a transient version (both
the infectious person and the susceptible person enter
an initially clean room) and a steady-state version (the
infectious person has been in the room long before the
susceptible person enters).
Upper-room germicidal irradiation (UVGI) uses wallmounted
or ceiling-suspended fi xtures in an occupied
CT =
G
()+
VF F
η
Transient concentration:
1
T ∫ ()C t dt
T
−kti
ACH ACH V


C =
S
1 ()− e
−+η
ACH ACHVF F t


Steady-state concentration:
G
()+ACH ACHη
VF F
V
C(t)= Concentration (# m-3) of airborne particles at time t(h)
G = Emission rate of droplet nuclei (# h-1)
V = Volume of space (m3)
ACHV = Q v / V = air-exchange rate due to ventilation (h-1)
ACHF = Q F / V = air-exchange rate due to fi ltration (h-1)
ηF
= Single-pass fi lter effi ciency of air fi lter
t = h
Q v
= Room ventilation rate (m3 h-1)
Q F = Recirculating airfl ow rate through the fi lter (m3 h -1)
room to treat the air above the occupants and kill microorganisms.
Louvers or shields are used to block the UV-C
from eyesight to keep the occupants safe. In 1937 Wells,
et al., successfully used upper-room UVGI to prevent the
epidemic spread of measles in suburban Philadelphia
day schools.8 Between 1969 and 1972 Riley and others
conducted model room studies to evaluate the use of
upper-room UVGI to reduce the concentration of aerosolized
test organisms in the lower room.8 In these tests,
mixing between the upper and lower room was shown
to be imperative for effective disinfection and that high
humidity reduced the effectiveness of the UVGI.8
Effective doses for UVGI have been established for a
wide range of microbial species, but some of these doses
were determined for organisms on Petri plates instead
of in aerosolized form and could overestimate the dose
required for inactivation.9 Viruses like infl uenza, smallpox
and adenovirus lack a cell wall and are more easily
inactivated than vegetative bacteria or spores.9 A dose
that inactivates Mycobacterium tuberculosis will be more
than adequate to inactivate most respiratory viruses.9
In spaces that are poorly ventilated, ceiling fans (at
low and medium speeds) can be used to promote the
vertical air movement and rapid transport of microorganisms
to the upper portion of the room and increase
the performance of the upper-room UVGI system.10
However, there is some indication that high fan speeds
don't increase performance, but can reduce the time
the microorganism stays in the UV irradiation fi eld and
increase the probability of inhalation before they are
inactivated.10
S E P T E M B E R 2 0 2 1 ashrae.o rg ASHRAE JOURNAL
39
http://ashrae.org

ASHRAE Journal - September 2021

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

Contents
ASHRAE Journal - September 2021 - Intro
ASHRAE Journal - September 2021 - Cover1
ASHRAE Journal - September 2021 - Cover2
ASHRAE Journal - September 2021 - 1
ASHRAE Journal - September 2021 - Contents
ASHRAE Journal - September 2021 - 3
ASHRAE Journal - September 2021 - 4
ASHRAE Journal - September 2021 - 5
ASHRAE Journal - September 2021 - 6
ASHRAE Journal - September 2021 - 7
ASHRAE Journal - September 2021 - 8
ASHRAE Journal - September 2021 - 9
ASHRAE Journal - September 2021 - 10
ASHRAE Journal - September 2021 - 11
ASHRAE Journal - September 2021 - 12
ASHRAE Journal - September 2021 - 13
ASHRAE Journal - September 2021 - 14
ASHRAE Journal - September 2021 - 15
ASHRAE Journal - September 2021 - 16
ASHRAE Journal - September 2021 - 17
ASHRAE Journal - September 2021 - 18
ASHRAE Journal - September 2021 - 19
ASHRAE Journal - September 2021 - 20
ASHRAE Journal - September 2021 - 21
ASHRAE Journal - September 2021 - 22
ASHRAE Journal - September 2021 - 23
ASHRAE Journal - September 2021 - 24
ASHRAE Journal - September 2021 - 25
ASHRAE Journal - September 2021 - 26
ASHRAE Journal - September 2021 - 27
ASHRAE Journal - September 2021 - 28
ASHRAE Journal - September 2021 - 29
ASHRAE Journal - September 2021 - 30
ASHRAE Journal - September 2021 - 31
ASHRAE Journal - September 2021 - 32
ASHRAE Journal - September 2021 - 33
ASHRAE Journal - September 2021 - 34
ASHRAE Journal - September 2021 - 35
ASHRAE Journal - September 2021 - 36
ASHRAE Journal - September 2021 - 37
ASHRAE Journal - September 2021 - 38
ASHRAE Journal - September 2021 - 39
ASHRAE Journal - September 2021 - 40
ASHRAE Journal - September 2021 - 41
ASHRAE Journal - September 2021 - 42
ASHRAE Journal - September 2021 - 43
ASHRAE Journal - September 2021 - 44
ASHRAE Journal - September 2021 - 45
ASHRAE Journal - September 2021 - 46
ASHRAE Journal - September 2021 - 47
ASHRAE Journal - September 2021 - 48
ASHRAE Journal - September 2021 - 49
ASHRAE Journal - September 2021 - 50
ASHRAE Journal - September 2021 - 51
ASHRAE Journal - September 2021 - 52
ASHRAE Journal - September 2021 - 53
ASHRAE Journal - September 2021 - 54
ASHRAE Journal - September 2021 - 55
ASHRAE Journal - September 2021 - 56
ASHRAE Journal - September 2021 - 57
ASHRAE Journal - September 2021 - 58
ASHRAE Journal - September 2021 - 59
ASHRAE Journal - September 2021 - 60
ASHRAE Journal - September 2021 - 61
ASHRAE Journal - September 2021 - 62
ASHRAE Journal - September 2021 - 63
ASHRAE Journal - September 2021 - 64
ASHRAE Journal - September 2021 - 65
ASHRAE Journal - September 2021 - 66
ASHRAE Journal - September 2021 - 67
ASHRAE Journal - September 2021 - 68
ASHRAE Journal - September 2021 - 69
ASHRAE Journal - September 2021 - 70
ASHRAE Journal - September 2021 - 71
ASHRAE Journal - September 2021 - 72
ASHRAE Journal - September 2021 - 73
ASHRAE Journal - September 2021 - 74
ASHRAE Journal - September 2021 - 75
ASHRAE Journal - September 2021 - 76
ASHRAE Journal - September 2021 - 77
ASHRAE Journal - September 2021 - 78
ASHRAE Journal - September 2021 - 79
ASHRAE Journal - September 2021 - 80
ASHRAE Journal - September 2021 - Cover3
ASHRAE Journal - September 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