United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-89/014 Jan. 1990
v°/EPA Project Summary
Evaluation of New
In-Facepiece Sampling
Procedures for Full and
Half Facepieces
Warren R. Myers and Richard W. Hornung
The manufacture, handling, and use
of new chemical substances often
require a level of personal protection
that includes respirators. Because of
the need for these respiratory pro-
tection devices, processes to eval-
uate penetration of full and half
facepiece, negative-pressure respira-
tors were studied.
The precision and bias were
determined for five methods of
sampling for inboard penetration
through different areas of the face
seal. The sampling procedures evalu-
ated were: continuous, low sampling
rate, flush on the respirator, mid-
nose-mouth probing (CLF); continu-
ous, high sampling rate, deep front-
of-mouth probing (CHD); pulsed,
exhalation, deep front-of-mouth prob-
ing (FED); exhalation valve discharge
(EVD); and pulsed, inhalation, deep
front-of-mouth probing (PID). The CLF
procedure represents current in-face-
piece sampling practice in the United
States.
Based on evaluation with nine full
facepiece respirators, the mean sam-
pling biases were CLF: -21%; CHD:
-3%; PED: 0.7%; EVD: -14%; and PID:
-12.3%. For five half facepiece res-
pirators, the mean sampling biases
were CLF: -26%; CHD: -13%; PED: -4%;
EVD: -2%; and PID: -24%. To some
extent, the location of the face seal
penetration, and the design of the
respirator affected the bias of each
method.
This Project Summary was devel-
oped by EPA's Risk Reduction Engi-
neering Laboratory, Cincinnati, OH, to
announce key findings of the research
project that is fully documented In a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
A variety of protective clothing and
equipment is often necessary to protect
workers during the manufacture, hand-
ling, and use of new chemical sub-
stances. In most cases where a need for
respiratory protection exists, air-filtering,
negative-pressure, full and half facepiece
respirators are recommended. Because
of the inherent danger of exposure to
such chemicals, extra care often must be
taken to ensure worker protection.
Various fit test procedures are used or
have been suggested for evaluating the
quantitative fit and protection of full and
half facepiece, negative-pressure respira-
tors. Recently published data has,
however, demonstrated that the proced-
ure commonly used in the United States
is subject to large sampling biases.
Factors that appear to contribute signifi-
cantly to this bias include: location and
depth of the sampling probe; location of
the face seal leak; whether the wearer is
breathing through the nose or the mouth;
the aerosol size selectivity of different
leak sizes; and the inspired air flow
patterns and air mixing produced by
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different facepiece designs. Consequent-
ly, the presently used test provides less
than the desired level of assurance that
full protection is being achieved.
This research sought to evaluate the
bias and precision of alternative in-
facepiece sampling procedures and
compare them with the CLF procedure
currently in wide use in the United States
for both full and half facepiece
respirators. The goal of the evaluation
was to identify and recommend, if
possible, an in-facepiece sampling
procedure with lower bias and greater
precision.
Test System
The system used to test the various
respirators consisted of an acetone vapor
generation and dilution system and an
air/acetone feed line to one of the leak
sites on the face seal of the respirator
test setup. Each respirator, equipped with
organic vapor cartridges, was mounted
on a headform manikin with an airtight
face seal. The headform could simulate
nose or mouth breathing at a relatively
constant rate between 18 and 19 cycles/
min, by the use of a breathing machine.
Leaks simulated by a hypodermic sy-
ringe needle were positioned in the
various areas of the full and half masks.
The syringe needle was connected to the
acetone system, and inboard flow of
acetone resulted from the negative
pressure created during each inhalation
cycle.
For pulsed sampling during inhalation
or exhalation, a pressure sensitive switch
activates a three-way solenoid valve
attached to the in-facepiece sampling
line. A calibrated flame ionization detec-
tor measured real-time acetone concen-
tration in the collected samples. The
"true" acetone concentration was meas-
ured in the line between the headform
and the breathing machine. The appa-
ratus is shown schematically in Figure 1.
Experimental Design
The experimental design for the full
facepiece respirators was a fixed effects
factorial model that considered three leak
sites, two leak sites, and five sampling
methods on nine models. The nine
selected models were those brands (with-
out nose cups) currently certified by
NIOSH: American Optical, Cesco, Glen-
dale, MSA, North, Pulmosan, Scott, USD,
and Willson.
Based on preliminary testing, the
(6) could best be measured as the
of the difference between the in-f
piece acetone concentration (C) and
"true" concentration (CX):
B = (6 - C/)C/
The experimental design was then si
as an analysis of variance with B a
dependent variable measured at d
nated levels of the four factors: leak
leak size, sampling method, and moc
For half facepiece respirators, 5 c
16 NIOSH-certified respirators
tested: American Optical, MSA, 5
USD, and Willson.
Sampling Methods and
Procedures
CLF Sampling Procedure
This is a continuous, low samplin
(1 L/min, during inhalation and exhal
procedure with the sampling i
mounted flush on the body of the
piece in the area between nose
mouth. The manikin headform is sel
simulate nose breathing.
Solenoid
Unbiased
Sample
Site
Breathing
Machine
Dilution Air
Flgun 1. Experimental test system used to evaluate the bias in different methods of sampling for inboard, face seal, penetration on h
full facepieces.
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3HD Sampling Procedure
This is a continuous, high sampling
rate (5 L/min during inhalation and
exhalation) procedure with the sampling
probe extended into the facepiece cavity
and located in front of the mouth. The
manikin simulates mouth breathing.
'ED Sampling Procedure
In this method, pulses of air (contam-
nated with acetone) are collected from
he facepiece only during exhalation
jsing a deep probe location. The manikin
imulates mouth breathing. It has been
Jetermined that sampling through the
srobe is not the same as sampling from
he exhalation valve of the respirator.
EVD Sampling Procedure
This method employs high rate (5
./min continuous sampling of the air
discharged through the exhalation valve
M the respirator whereas the manikin
imulates mouth breathing.
3ID Sampling Procedure
This procedure collects a pulse of air
Juring inhalation, with the use of a deep
Drobe location.
Results and Discussion
Because problems were encountered
with the small leak size in the full
acepiece respirators, data analysis was
limited to the larger leak size. This
reduced the number of variables to three.
Note that the test system did not
simulate any lung retention; this could
increase average sampling bias values.
Further, the test program was done with
the use of a vapor challenge agent; very
different results, with larger bias values,
might be obtained with conventional oil
mist or sodium chloride fit-tests or tests
in workplace environments.
Because the five methods of testing
varied considerably, statistical analyses
were computed separately for each
method. This study confirmed earlier
results that the sampling bias is
influenced by the leak location. It also
indicated that the design of the facepiece
influences the effect of leak location.
Of the five methods, the FED sampling
procedure consistently gave the lowest
sampling bias and the best precision in
the full facepiece respirator tests. It also
was less sensitive to the location of leak
than was the CHD procedure. The EVD
and PID procedures, although not as
good as the RED and the CHD sampling
procedures, still gave smaller (and ap-
proximately equivalent) sampling biases
than did the conventional CLF procedure.
Based on a combined measure of pre-
cision and bias in which each factor is
given equal weight (see Table 1), the
ranking of the five methods would be:
RED > CHD > EVD > PID > CLF
With the half facepiece respirators, the
strongest interaction existed between
sampling method and manufacturer
(design). Three-way interactions among
manufacturer, leak size, and leak location
were also significant in all but the EVD
procedure. Although not as clear as with
the full face pieces, the RED procedure
again produced better mean sampling
biases than did the conventional CLF
procedure or the CHD procedure. Sur-
prisingly, the EVD procedure produced
much smaller biases with the half
facepieces than it had with the full
facepieces and was approximately equiv-
alent to the RED procedure. Both the PID
procedure and the conventional CLF
procedure produced poorer results in the
statistical analysis. Table 2 summarizes
the precision and bias for the half face-
pieces. Based on the combined results,
the methods would be ranked in the
following order:
EVD > RED > CHD > CLF > PID
Based on the data with both half and
full facepiece respirators, the RED sam-
pling procedure appears to be signif-
icantly more.precise and less biased than
the conventional CLF sampling proce-
dure now widely used in the United
States. On that basis, it should be
considered as a replacement for quan-
titative fit testing. Before a procedure
change is made, however, it may be
necessary to learn more about the RED
procedure. For example, whereas the
testing in this study was done at a 5
L/min sampling rate during exhalation,
the effect of lower flowrates on bias
needs to be evaluated, as will the effect
of relative humidity on test validity and
the effect of lung retention.
Conclusions and
Recommendations
Several alternative sampling methods
for in-facepiece respirator testing were
evaluated and compared with a method
widely used in the United States. Based
on these tests, two of the alternative
methods are clearly superior to the
conventional CLF (continuous sampling,
low flow, flush probe) method in sam-
pling precision and bias. Of these, the
RED method (pulsed sampling, exhala-
tion, deep probe) appears to be superior
for both full and half facepiece respira-
tors. The RED procedure, however, will
require further validation and equipment
modifications before it can be substituted
for the current test method. Until that is
done, another of the alternatives, the
CHD sampling procedure (continuous
sampling, high flow, deep probe), should
replace the conventional method with the
use of CLF equipment.
Table 1. Test Results for Five Procedures on Nine Full Facepieces
Procedure
Precision
SO
Mean Bias
§
Combined
Measure"
Ft
CLF
CHD
PED
EVD
PID
81
81
81
80
81
14.0
11.8
5.0
11.9
21.0
-21.3
-3.4
0.7
-14.2
-12.3
25.5
12.3
5.0
18.5
24.3
Table 2.
"R = (SO2 + B2)112
Test Results for Five Procedures on Five Half Facepieces
Procedure
CLF
CHD
PED
EVD
PID
n
60
60
60
60
60
Precision
SO
74.0
11.7
5.0
3.0
29.2
Mean Bias
8
-25.9
-12.5
-3.7
-2.3
-24.1
Combined
Measure'
R
29.4
17.1
6.9
3.8
37.9
•R = (SD2 * 82; "2
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The full report was submitted in ful-
fillment of Interagency Agreement No.
DW 75931135-01-2 by The National
Institute for Occupational Safety and
Health, under the sponsorship of the U.S.
Environmental Protection Agency.
Warren R. Myers is now with West Virginia University, Morgantown, WV 26506; and
Richard W. Hornung is with the National Institute for Occupational Safety and
Health, Cincinnati, OH 45226.
Raymond M. Frederick is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of New In-Facepiece Sampling Proce-
dures for Full and Half Facepieces," (Order No. PB 89-181 2421 AS; Cost: $13.95,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Releases Control Branch
Risk Reduction Engineering Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, New Jersey 08837
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
U-S.QFRCiALMAlL
Official Business
Penalty for Private Use $300
EPA/600/S2-89/014
000085B33 I0,
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