Total Inward Leakage Measurement of Particulates for N95 Filtering Facepiece Respirators--A Comparison Study

Abstract

National Institute for Occupational Safety and Health (NIOSH) certified particulate respirators need to be properly fit tested before use to ensure workers' respiratory protection. However, the effectiveness of American National Standards Institute-/Occupational Safety and Health Administration (ANSI-/OSHA)-accepted fit tests for particulate respirators in predicting actual workplace protection provided to workers is lacking. NIOSH addressed this issue by evaluating the fit of half-mask particulate filtering respirators as a component of a program designed to add total inward leakage (TIL) requirements for all respirators to Title 42 Code of Federal Regulations Part 84. Specifically, NIOSH undertook a validation study to evaluate the reproducibility of the TIL test procedure between two laboratories. A PortaCount® was used to measure the TIL of five N95 model filtering facepiece respirators (FFRs) on test subjects in two different laboratories. Concurrently, filter efficiency for four of the five N95 FFR models was measured using laboratory aerosol as well as polydisperse NaCl aerosol employed for NIOSH particulate respirator certification. Results showed that two N95 models passed the TIL tests at a rate of ~80-85% and ~86-94% in the two laboratories, respectively. However, the TIL passing rate for the other three N95 models was 0-5.7% in both laboratories combined. Good agreement (≥83%) of the TIL data between the two laboratories was obtained. The three models that had relatively lower filter efficiency for laboratory aerosol as well as for NaCl aerosol showed relatively low TIL passing rates in both laboratories. Of the four models tested for penetration, one model with relatively higher efficiency showed a higher passing rate for TIL tests in both laboratories indicating that filter efficiency might influence TIL. Further studies are needed to better understand the implications of the data in the workplace.

Full text

Ann. Occup. Hyg., 2014, Vol. 58, No. 2, 206–216
doi:10.1093/annhyg/met054
Advance Access publication 9 October 2013
Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2013.
206 •
Total Inward Leakage Measurement of
Particulates for N95 Filtering Facepiece
Respirators—A ComparisonStudy
SamyRengasamy*, Gary F.Walbert, William E.Newcomb,
KimberlyFaulkner, Mathi M.Rengasamy, Jeremy J.Brannen and
Jonathan V.Szalajda
National Institute for Occupational Safety and Health, National Personal Protective Technolog y Laboratory, 626 Cochrans Mill Road,
PO Box 18070, Pisburgh, PA 15236, USA
*Author to whom correspondence should be addressed. Tel:+412-386-6853; fax : +412-386-4089;
e-mail: rda5@cdc.gov
Received 9 April 2013; revised 21 June 2013; revised version accepted 3 August 2013.
AbstrAct
National Institute for Occupational Safety and Health (NIOSH) certied particulate respirators need
to be properly t tested before use to ensure workers’ respiratory protection. However, the eectiveness
of American National Standards Institute-/Occupational Safety and Health Administration (ANSI-/
OSHA)-accepted t tests for particulate respirators in predicting actual workplace protection provided
to workers is lacking. NIOSH addressed this issue by evaluating the t of half-mask particulate lter-
ing respirators as a component of a program designed to add total inward leakage (TIL) requirements
for all respirators to Title 42 Code of Federal Regulations Part 84. Specically, NIOSH undertook a
validation study to evaluate the reproducibility of the TIL test procedure between two laboratories.
APortaCount® was used to measure the TIL of ve N95 model ltering facepiece respirators (FFRs)
on test subjects in two dierent laboratories. Concurrently, lter eciency for four of the ve N95
FFR models was measured using laboratory aerosol as well as polydisperse NaCl aerosol employed for
NIOSH particulate respirator certication. Results showed that two N95 models passed the TIL tests
at a rate of ~80–85% and ~86–94% in the two laboratories, respectively. However, the TIL passing rate
for the other three N95 models was 0–5.7% in both laboratories combined. Good agreement (≥83%)
of the TIL data between the two laboratories was obtained. e three models that had relatively lower
lter eciency for laboratory aerosol as well as for NaCl aerosol showed relatively low TIL passing
rates in both laboratories. Of the four models tested for penetration, one model with relatively higher
eciency showed a higher passing rate for TIL tests in both laboratories indicating that lter eciency
might inuence TIL. Further studies are needed to beer understand the implications of the data in
the workplace.
Keywords: aerosol; faceseal leakage; lter penetration; N95 ltering facepiece respirators; total
inward leakage
Head1=Head2=Head1=Head2_Aer_Head1

Total inward leakage measurement of particulates • 207
IntroductIon
e use of appropriate respirators approved by the
National Institute for Occupational Safety and Health
(NIOSH) is one method for reducing occupational
exposure to airborne particles if engineering and
administrative controls are not sucient. e major
factors that determine the level of respiratory protec-
tion are the lter eciency and respirator t. For cer-
tication of particulate respirators, NIOSH requires a
lter eciency test but no test to assess faceseal leakage
of particulates. Faceseal leakage created during respira-
tor use is known to compromise respiratory protection.
To address this issue, Occupational Safety and Health
Administration (OSHA) requires a t test of tight-
ing respirators prior to use in workplaces (OSHA,
1998a). Several studies have reported that t testing
largely improves the respiratory protection level of test
subjects (Coey et al., 1999; Campbell et al., 2001;
Coey etal., 2004; Lawrence etal., 2006). On the other
hand, t test–passed respirators in some studies have
failed to provide expected level of protection (Duling
etal., 2007; Lee etal., 2008). For respiratory protec-
tion, NIOSH has approved three classes (95, 99, and
100)of particulate lters with lter eciencies of 95,
99, and 99.97%. All three classes of NIOSH-approved
ltering facepieces have been assigned a protection
factor (APF) of 10 (OSHA, 2006). An APF is dened
as the minimum respiratory protection expected of a
properly functioning respirator when used in a respira-
tory program. On the other hand, European standard
has assigned APF values of 4, 10, and 20 to FFP1,
FFP2, and FFP3 particulate lters, respectively, based
on eciency, hazard level, and occupational exposure
limit (European Standard, 2005).
Evaluation of particulate respirators with either
Bureau of Mines (BOM) or NIOSH approval has been
reviewed (Campbell etal., 2001; Spelce, 2009). BOM
employed a ‘coal dust test’ as one of the methods for
the evaluation of particulate respirators under Title 30
Code of Federal Regulations (CFR) Part 14 Schedule
21 (BOM, 1934). ree individuals donned respirators
and did a regimen of moderate work and rest periods
for 30 min in a room full of bituminous coal dust. Aer
which, their forced nasal discharge, sputum, nasal cavi-
ties, and face were examined for black particulates. e
coal dust test can be assumed to be equivalent to the
total inward leakage (TIL) measurement comprised
of lter penetration and leakage through the faceseal
and other components including exhalation valves.
Requirements were similar under Title 30 CFR Part 14
Schedule 21A in 1955 (BOM, 1955). By 1965 when
Title 30 CFR Part 14 Schedule 21B was approved,
coal dust was specied to be blown gently into the test
subjects’ face and the exercises were omied (BOM,
1965). When the respirator certication requirements
were incorporated into Title 30 CFR Part 11, the coal
dust test was abolished (NIOSH and BOM, 1972).
For Title 30 CFR Part 11 Schedule 21C, the BOM
and NIOSH decided to use isoamyl acetate instead
of coal dust to qualify the ability of all tight ing and
some loose ing respirators to t wearers (NIOSH
and BOM, 1972). ere was only one problem with
this; isoamyl acetate is an organic vapor which is not
removed by a dust, mist, fume, or high eciency par-
ticulate lter. NIOSH dealt with this problem by test-
ing particulate respirators modied to remove organic
vapors. It was incorrectly assumed that a particulate
respirator could be ed with a vapor-removing ele-
ment without changing its weight, resistance, or ing
characteristics and therefore be used as a surrogate for
testing purposes.
When Title 42 CFR Part 84 was promulgated in
1995, this non-validated test of questionable eec-
tiveness was also eliminated (NIOSH, 1995). In the
preamble of Title 42 CFR Part 84, it is stated, ‘e
purpose of t testing in the certication program has
been to assure that respirators have generally good
face ing characteristics. However, at this time,
NIOSH does not have studies that dene the eec-
tiveness of either the isoamyl acetate or American
National Standards Institute-/Occupational Safety
and Health Administration (ANSI-/OSHA)-
accepted t tests in predicting actual workplace pro-
tection provided to workers. NIOSH is presently
conducting research for this purpose. …. NIOSH
will address issues associated with face-t ecacy in
a separate module upon completion of the necessary
research’.
In 2004, NIOSH developed a program concept for
TIL performance requirements and test methods for
personal protective equipment including all classes
of respirators and protective garments (NIOSH,
2004). Subsequently, NIOSH evaluated half-mask
particulate ltering respirators as a component of
this program designed to add TIL requirements for
all respirators to Title 42 CFR Part 84. Based on this

208 • Total inward leakage measurement of particulates
evaluation, NIOSH published a Notice of Proposed
Rulemaking (NPRM) for TIL requirements for half-
mask particulate ltering respirators (NIOSH, 2009).
Subsequently, NIOSH held two public meetings to
gain stakeholder input on the proposed rulemak-
ing, and a NIOSH docket was opened for comments
(NIOSH, 2010). Many of the comments concerned
the reproducibility of the test procedure that had been
developed and posted to the docket (NIOSH, 2008).
Variability of the test procedure in dierent laborato-
ries was one of the issues raised. As a result, NIOSH
undertook this validation study to evaluate the repro-
ducibility of the test procedure.
In this study, a PortaCount® Pro+ (Model 8038,
TSI, Inc. Shoreview, MN; a condensation particle
counter) was chosen as the method matching the
requirements published in the TIL NPRM (NIOSH,
2009). e reason for choosing this method over other
methods is discussed in the preamble of the NPRM.
e condensation particle counting method has been
widely used for quantitative t testing because of its
simplicity and portability. TIL was measured for
test subjects in two laboratories (Laboratory 1 and
Laboratory 2) located in the NIOSH facility. Five
N95 ltering facepiece respirator (FFR) models were
selected for the comparison of TIL tests in the two
test laboratories. Concurrently, four of the ve N95
models were also tested for lter eciency against
Laboratory 2 ambient aerosol. e comparison of the
TIL results between the two test laboratories and the
correlation of the TIL values to lter eciency of the
test respirators are discussed.
MAterIAls And Methods
Respirator selection
Five N95 FFR models were tested in the TIL proto-
col validation study (Table 1). e respirator mod-
els tested in the study include 3M (Model 8000), 3M
(Model 9210), Kimberly–Clark (Model 170/174),
Sperian–Willson (Model SAF-T-FIT, 10FL), and 3M
(Model 8511), which were labeled as A, B, C, D, and
E, respectively. Only one model (3M 8511)had an
exhalation valve. Prior to this study, NIOSH con-
ducted benchmark tests using several N95 model
FFRs to measure TIL in 2005. From the test results,
respirator models with wide range of TIL perfor-
mances were selected for thisstudy.
Test subjects
irty-ve subjects were tested for TIL measure-
ment with each of the ve FFR models in both test
laboratories. e NIOSH bivariate panel was used
for placement of test subjects in specic face length
by face width cells (Zhuang etal., 2008). is study
was approved by the NIOSH Human Subject Review
Board, and all subjects gave wrien consent to
participate.
Laboratory aerosol specications for
TIL testing
A minimum laboratory particle concentration of 1000
particles cm−3 was used during TIL testing. A par-
ticle generator (TSI Model 8026)was employed, as
needed, to supplement laboratory particle concen-
tration levels with NaCl aerosol. Ambient laboratory
aerosol concentration (particles cm−3) measured by
the PortaCount in Laboratory 1 ranged between 1310
and 8740 (average 3010)and in Laboratory 2 ranged
between 1370 and 10100 (average 5410).
TIL testing
Subject testing
Test subjects were randomly directed for TIL testing in
either Laboratory 1 or Laboratory 2 to start. e sub-
jects subsequently travelled (~300 m) to Laboratory 2
or Laboratory 1, respectively, and were tested for TIL
following the identical donning procedure. Dierent
test operators administered the TIL testing in each of
the two laboratories and each was an experienced t
tester. is study was double blind in the sense that
the test operators in either laboratory did not know
the results obtained by the other laboratory. All test-
ing was performed in accordance with Standard
Test Procedure RCT-APR-STP-0068 (posted under
NIOSH Docket No. 36; NIOSH, 2007a), with few
exceptions. ese exceptions included increasing the
minimum required particle count from the specied
500 particles cm−3 to 1000 particles cm−3 and operat-
ing the PortaCount with the N95 mode turned o to
measure TIL as opposed to measuring only leakage
through faceseal interface.
Subjects were trained using the manufacturer’s user
instructions on the proper donning and user seal-check
procedures for each model. Subjects wore the FFR for
a 5-min acclimatization period before the t test. Each

Total inward leakage measurement of particulates • 209
subject subsequently connected the PortaCount sam-
ple line to the connector on the respirator, donned the
FFR, and made any necessary adjustments to the FFR
until they felt they had achieved a good t and could
subsequently pass the user seal check without detect-
ing a faceseal leak. Test administrators assured that the
FFR was being properly donned by the test subject and
provided whatever training was necessary to assure
conformance to the user’s instructions while respira-
tor donning and adjustment was taking place. When
ready, the subjects gave the test administrator an indica-
tion that she or he was ready to start the test. e drag/
weight of the sample tubing and its eect on the FFR t
was minimized by the test subject holding the sample
line with one hand away from the front of their chest.
Subjects performed the eight exercises described in
the standard OSHA t test protocol (OSHA, 1998b).
ese eight exercises were performed in the following
order: (i) normal breathing, (ii) deep breathing, (iii)
turn head side to side (iv) move head up and down, (v)
speak out loud (recitation of the ‘rainbow’ passage), (vi)
reach for oor and ceiling, (vii) grimace, and (viii) nor-
mal breathing. Aharmonic mean of the t factors (FFs)
measured for the eight exercises was determined by the
PortaCount. At the end of the test, the subject removed
the FFR and aer a 5-min break redonned the same
FFR for the next test. ree replicate tests were done in
succession.
Two similar PortaCounts were used to measure the
FF, the ratio of ambient aerosol concentration (Cout)
to in-mask particle concentration (Cin) in the two test
laboratories. AFitPro Fit Test soware (TSI) was used
to provide a fully automated t test processing, data
recording, and data storage during the testing. Test
data, including test subject and respirator identiers
were downloaded into a pre-established database and
were accessed aer the test for analysis. Test data were
also recorded manually for immediate review by pro-
ject personnel.
TIL calculation
TIL was calculated from the FF obtained by the
PortaCount based on the inverse relationship as
shownbelow.
TIL
FF
=
100%
To pass the test, NIOSH has proposed a TIL of ≤1%
in any one of the three donnings of each FFR tested
on each subject. ATIL value of ≤1% is equivalent to
a FF value of ≥100 obtained for subjects performing
the OSHA-prescribed exercises for passing the t test.
Further information on the criteria for passing the TIL
test has been described (NIOSH, 2008).
Laboratory aerosol size distribution measurement
Two Scanning Mobility Particle Sizers (SMPS Model
3081, TSI) were used to measure the size distribution
of particles in the 10–700 nm size range in the two lab-
oratories. e SMPS was programed to scan the parti-
cle size distribution for 135 s, three times, every hour
from 8:00 AM to 4:00 PM, Monday through Friday.
From the SMPS scans, the average count median
diameter (CMD) of laboratory aerosol was obtained.
Filter penetration
Only four N95 respirator models were tested
because one model (3M 8511) was not available
during the initial part of the study. Filter penetra-
tion was measured by two dierent methods: (i) a
Table1. TIL for N95 FFR models measured on human subjects using a PortaCount Pro
Respirator Number of subjects tested Subjects passing TIL test (TIL ≤ 1)(%)
Laboratory 1 Laboratory 2
A 35 0 2.9
B 35 80.0 85.7
C 35 5.7 2.9
D 35 2.9 5.7
E 35 85.7 94.3

210 • Total inward leakage measurement of particulates
particle-number-based method using ambient aerosol
in the TIL test Laboratory 2, similar to the number-
based PortaCount method used for TIL measurement
and (ii) a particle mass-based method using polydis-
perse NaCl aerosols similar to the NIOSH particulate
respirator certication method.
Particle-number-based penetrationtest
Instantaneous penetration against ambient
Laboratory 2 aerosol was measured using a test set-up
as shown in the schematics (Fig.1). A Plexiglas box
(20 × 20 × 10 cm) similar to the one described previ-
ously (Rengasamy etal., 2008) was used to measure
lter penetration with a respirator mounted on the
boom plate. Asilicon sealant was used to seal the top
and boom plates to make the Plexiglas box airtight.
e top and boom holes of the plates were xed to
inlet and outlet tubes (2.0 cm diameter and 10 cm
long). An aerosol sampling tube (0.5 cm diameter)
was aached to the inlet and outlet close (2.5 cm)
to the Plexiglas box. e sampling tubes were con-
nected to two ultrane condensation particle coun-
ters (UCPCs, TSI 2205) to measure the upstream
and downstream aerosol concentrations. e boom
outlet was connected to a vacuum line through a mass
ow meter. e desired ow rate was obtained by
adjusting the vacuum.
Five samples from each model were tested in the
morning (8:30–9:30 AM), stored, and then tested in
the aernoon (2:30–3:30 PM), and the average pene-
tration was obtained. Briey, Laboratory 2 aerosol was
passed through the respirator in the test box, and the
particle number concentration upstream and down-
stream of the respirator was measured simultaneously
aer 1-min equilibration time at constant test ow
rates of 30 and 85 l min-1, representing moderate work
rate and the NIOSH particulate respirator certica-
tion test ow rate, respectively. Percentage penetration
was obtained from the ratio of the aerosol concentra-
tion downstream to upstream and multiplied by 100.
From the penetration values, the lter eciencies for
the four models were assessed.
Particle mass-based penetrationtest
Penetration was also measured using an Automated
Filter Tester (TSI 8130)similar to the NIOSH par-
ticulate respirator certication method (NIOSH,
2007b). A Plexiglas test box (20 × 20 × 10 cm) was
used to measure polydisperse NaCl aerosol penetra-
tion as described previously (Rengasamy etal., 2008).
e boom plate was replaced by a plate mounted
with an FFR tested previously for Laboratory 2 aero-
sol penetration. e Plexiglas box containing the res-
pirator was placed in between the two lter chucks of
the TSI 8130 and aligned to keep the top and boom
plate holes facing the upstream and downstream lter
chucks, respectively. Penetration was measured under
airtight conditions using the polydisperse NaCl aero-
sol (CMD; 75 ± 20 nm) generated by the TSI 8130.
Initial penetration was measured for 1 min at 30 l
min−1 as well as 85 l min−1 ow rates.
Data analysis
TIL pass/fail results were calculated. Agreement in
TIL pass/fail results between the two laboratories
were estimated using kappa statistics with STATA sta-
tistical soware (College Station, TX). Akappa statis-
tic is an estimate of the level of agreement of the results
obtained between the two laboratories beyond that
which could be expected by chance alone. Akappa sta-
tistic that is greater than zero but less than 0.40 is poor
agreement, whereas a kappa between 0.40 and 0.75 is
fair-to-good agreement, and a kappa >0.75 is excellent
agreement (Fleiss, 1981).
results
TILdata
Table1 shows the TIL data obtained for the dierent
N95 models tested in Laboratory 1 and Laboratory
1 Schematic of the ltration test set-up used for
measuring laboratory aerosol lter penetration.

Total inward leakage measurement of particulates • 211
2. Of the ve N95 models tested, models B and E
passed the TIL test at higher percentage levels. irty-
ve human subjects tested with model B in Laboratory
1 as well as in Laboratory 2 passed 80 and 85.7% of
tests, respectively. Similarly, model E FFRs showed
85.7 and 94.3% passing results in Laboratory 1 and
Laboratory 2, respectively. However, the percentage
of TIL passes for A, C, and D FFR models was small
(0–5.7%) in the two test laboratories. e TIL data
obtained for A, B, C, D, and E models showed 97, 83,
97, 97 and 91% agreement between the two laborato-
ries, respectively.
Figure2 shows the proportion of the 35 test sub-
jects, according to their pass or fail status on the TIL
test procedure in the two laboratories, for each of the
ve dierent N95 FFRs and corresponding kappa
statistics. e proportion of subjects who showed
agreement between the two laboratories (either passed
or failed at both) was highest for models A, C, and D at
0.971. e proportion of subjects who showed agree-
ment between the two laboratories (either passed or
failed at both) was next highest for models B and E at
0.829 and 0.914, respectively.
e kappa statistics for FFR models B, C, D, and
E ranged from 0.40 to 0.65, indicating fair-to-good
agreement between the two laboratories (P <0.01
for all). e kappa statistic for FFR model A was
zero, indicating that there was no evidence that the
observed agreement was any dierent than would be
expected by chance alone.
Laboratory aerosol size distribution
Figures 3 and 4, top panels show the size distribu-
tion of aerosol ranging from 20 to 700 nm obtained in
Laboratory 2 on dierent days. In general, the CMD
for ambient Laboratory 2 aerosol measured in the
morning was smaller than the values obtained in the
aernoon. On the other hand, on Day 5, the CMD
for laboratory aerosol was larger (CMD 127.4 nm) in
the morning than in the aernoon (CMD 86.6 nm;
Fig.5, top panel). Ambient aerosol size distribution
for all test days showed CMD values of 82 ± 19 nm in
Laboratory 1, and 131 ± 23 nm in Laboratory2.
Filter penetration
Particle-number-based penetration measured against
ambient Laboratory 2 aerosols on ve dierent days
at two dierent ow rates are shown in Figs 3–5 (bot-
tom panels). Penetration values for model B were
relatively lower than the penetrations for model A, C,
and D.Similar results were obtained for polydisperse
NaCl aerosols using a mass-based method at two dif-
ferent ow rates (Fig. 6). Based on the penetration
values obtained in the tests, model B was considered
as a relatively higher eciency model than models A,
C, andD.
dIscussIon
In this study, 35 human subjects tested with ve N95
model FFRs showed consistent TIL results in two
dierent test laboratories. Respirator models that
showed higher percentage of TIL pass in Laboratory 1
also had higher percentage of TIL pass in Laboratory
2. For example, N95 FFR models B and E showed
2 e proportion of 35 test subjects, according to
their pass or fail status on the TIL test procedure in
two laboratories, for ve dierent N95 model ltering
facepiece respirators and corresponding kappa statistics.

212 • Total inward leakage measurement of particulates
percentage of TIL passes ≥80% in both laboratories.
On the other hand, models A, C, and D had a simi-
lar percentage (0–5.7%) of TIL passes in the two test
laboratories. Moreover, TIL data measured for all ve
FFR models showed ≥83% agreement between the
two laboratories. Incorporation of TIL as part of the
respirator certication process may provide a beer
understanding on the level of protection expected in
workplaces.
Filter eciency appears to inuence the TIL
obtained for FFRs. e ltration eciency for model
B FFRs against TIL test laboratory aerosol as well as
NaCl aerosol employed in the NIOSH particulate l-
ter certication test were higher than the other three
models. Both the ltration eciency and the percent-
age of TIL passes were higher for model B than for
models A, C, and D showing an association between
lter eciency and TIL passes. e results obtained
in the study are consistent with the ndings reported
previously (Han and Lee, 2005). In that study, TIL
values for Korean half-masks and three classes of FFRs
with human subjects were measured. Among the three
classes of FFRs, average TIL values for ‘top class’ (l-
ter penetration < 1.0%) FFRs were 5.0%. However,
the TIL values for FFRs certied with higher lter
penetrations (‘rst class’: <6.0% and ‘second class’:
<20.0%) were ~2 times higher than the TIL values
obtained for ‘top class’ FFRs. e results from these
studies show that relatively higher eciency FFRs
produce lower TIL values.
To beer understand the inuence of lter e-
ciency, TIL was measured under controlled conditions
in our previous study (Rengasamy and Eimer, 2012a).
Four N95 models were used to measure the TIL with
a breathing manikin at dierent articially introduced
leaks and breathing minute volumes. Results showed
that relatively higher eciency N95 models also had
lower TIL values for the dierent size particles indicat-
ing the lter eciency dependence of TIL. Similar nd-
ings were obtained in another study which measured
3 Laboratory aerosol size distribution obtained with a SMPS (top panels),
and average penetration of morning (AM) and aernoon (PM) tests for
four N95 model FFRs using two UCPCs at 30 l min-1 ow rate (boom
panels) on two dierent test days.

Total inward leakage measurement of particulates • 213
the protection factor (PF, an inverse function of TIL)
of respirators (Liu et al., 1993). ese authors devel-
oped a theoretical expression for PF based on lter
penetration, leakage, and ow rate and made a com-
parison with experimental results. Relatively less-pene-
trating 10-nm monodisperse NaCl particles were used
to measure particle leakage using a manikin. Two rela-
tively lower eciency dust–mist respirators and one
higher eciency dust–mist–fume/radionuclide respi-
rator were tested for penetration with controlled leak
holes at three dierent steady ow rates. eir results
showed that the higher eciency respirator provided
a higher PF value than the lower eciency respirators.
Overall, the lter eciency dependence of TIL may be
relevant to respiratory protection in real workplaces.
Filter penetration and faceseal leakage pathways
contribute to the TIL, which is inversely related to res-
piratory protection (Han and Lee, 2005; Grinshpun
etal., 2009; Rengasamy and Eimer, 2012a). Grinshpun
etal. (2009) showed that the number of particles pass-
ing through faceseal leakage far exceeded the number of
particles that penetrate through the lter medium. Filter
penetration is minimal or insignicant once leaks are
introduced in the facemask. However, results obtained in
our laboratory showed that lter penetration is critical to
the TIL of dierent size particles (Rengasamy and Eimer,
2012a). In that study, four N95 model FFRs with and
without electrostatic charge were tested for TIL using a
breathing manikin under controlled leak conditions. e
most penetrating particle size (MPPS) was ~45 nm for
FFRs with charge and ~150 nm for the charge removed
FFRs under sealed condition with no leaks. With increas-
ing articial leak sizes, TIL for dierent size particles
increased, whereas the MPPS for the respective FFR
groups remained the same. Results showed that faceseal
leakage indiscriminately allowed all size particles to enter
and exit the respirator, while lter penetration assigned
the TIL for dierent size particles. is explains how the
4 Laboratory aerosol size distribution obtained with a SMPS (top panels),
and average penetration of morning (AM) and aernoon (PM) tests
for four N95 model FFRs using UCPCs at 85 l min-1 ow rate (boom
panels) on two dierent test days.

214 • Total inward leakage measurement of particulates
relatively higher eciency (relatively lower penetration)
N95 model B could produce lower TIL values than the
relatively lower eciency (higher penetration) models A ,
C, and D tested in thestudy.
e size distribution of laboratory aerosol may inu-
ence lter penetration of test respirators. e CMD
of ambient aerosol in Laboratory 2 was smaller in the
morning than in the aernoon on many days, while an
opposite trend was observed on other days. However,
the change in the size distribution of particles between
morning and aernoon did not appear to aect the
average penetration of N95 models measured by
the number-based method as well as the mass-based
method on dierent test days. One exception was that
the penetration values measured by the particle-num-
ber-based UCPC method against laboratory aerosol
were higher than the mass-based penetrations. is can
partly be explained by the dierence in the test methods
(Biermann and Bergman, 1988; Rengasamy etal., 2011;
Rengasamy and Eimer, 2012b). e UCPC measures
the particle numbers giving equal importance to the dif-
ferent size particles, whereas the light scaer intensity
measured by the TSI 8130 photometer is dependent on
the particle mass. e CMD of NaCl aerosol produced
by the TSI 8130 is ~75 nm. However, the TSI 8130
photometer employed for measuring lter penetration
is less sensitive to particles below 100 nm size which
have no signicant mass. Because of this, the penetra-
tion values measured for NIOSH-approved FFRs by the
particle-number-based method are several-fold higher
than the values obtained by the photometric method
(Rengasamy etal., 2011; Rengasamy and Eimer, 2012b).
lIMItAtIons
Limitations of the study include that the test subjects as
well as the test operators are experienced in their role as
they have participated in other t test studies previously.
ese factors could have maximized the agreement
in the results between the two laboratories. Only ve
N95 model FFRs were employed to measure the TIL,
of which only four N95 models were tested for lter
eciency. e four models tested for lter eciency in
the study do not have exhalation valves. Additional FFR
models with and without exhalation valves need to be
tested for lter penetration and TIL to conrm the pres-
ence of an exhalation valve does not impact the relation-
ship between lter penetration and TIL. Acomparison
of the mean or median TIL values for each subject in the
two laboratories is desirable, but it is beyond the scope
of the study. In this study, TIL was measured in two
laboratories located in the same NIOSH facility. Amore
realistic reproducibility test should involve laboratories
of two dierent research groups. Nevertheless, the TIL
data for human subjects and the lter eciency of respi-
rators obtained in the study has a potential implication
for respiratory protection in workplaces.
5 Laboratory aerosol size distribution obtained with
a SMPS in the morning and aernoon (top panel)
and average lter penetration values for four N95
model FFRs measured using two UCPCs (middle and
boom panels) on Day 5.

Total inward leakage measurement of particulates • 215
conclusIons
e data obtained for ve N95 model FFRs tested
with human subjects conrmed the reproducibility
of the TIL test procedure in the two test laborato-
ries. e TIL results for N95 models B and E passed
~80–85% of tests in Laboratory 1 and ~86–94% of
tests in Laboratory 2. Furthermore, the percentage
of TIL passes for the other three N95 models was
relatively small (0–5.7%) in both test laboratories.
Agood agreement (≥83%) of the TIL data between
the two laboratories was obtained. Of the four N95
models tested for lter penetration, the eciency of
one model was relatively higher than the other three
models. e relatively higher eciency model also
showed higher TIL passing rates than the other three
models. e data indicate that lter eciency might
inuence the TIL for test subjects using N95 FFRs.
Overall, the data suggest that TIL test may be repro-
ducible between dierent laboratories, as long as each
laboratory meets the test criteria.
AcknowledgeMents
e authors acknowledge NIOSH colleagues includ-
ing William King, Jay Parker, and Christopher Coey
for their useful suggestions and critical review of the
manuscript. is research work was supported by
NIOSH funding.
dIsclAIMer
Mention of commercial product or trade name does
not constitute endorsement by the National Institute
for Occupational Safety and Health. e ndings and
conclusions of this report are those of the authors and
do not necessarily represent the views of the National
Institute for Occupational Safety and Health.
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