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chart or computer or integrator) shall be kept to shall be measured in the test chamber prior to
a minimum. There shall be a clear association
between the occurrence of an event and its be-
ing recorded.
(10) The sampling line tubing for the test
chamber atmosphere and for the respirator
sampling port shall be of equal diameter and
of the same material. The length of the two
lines shall be equal.
(11) The exhaust flow from the test chamber
shall pass through an appropriate filter (i.e.,
high efficiency particulate filter) before release. obtained prior to the actual start of testing.
(12) When sodium chloride aerosol is used, the
relative humidity inside the test chamber shall
not exceed 50 percent.
13) The limitations of instrument detection
shall be taken into account when determining
the fit factor.
(14) Test respirators shall be maintained in
proper working order and be inspected regu-
larly for deficiencies such as cracks or missing
valves and gaskets.
(b) Procedural Requirements.
(1) When performing the initial user seal check
using a positive or negative pressure check, the
sampling line shall be crimped closed in order
to avoid air pressure leakage during either of
these pressure checks.
(2) The use of an abbreviated screening QLFT
test is optional. Such a test may be utilized in
order to quickly identify poor fitting respira-
tors that passed the positive and/or negative
pressure test and reduce the amount of QNFT
time. The use of the CNC QNFT instrument in
the count mode is another optional method to
obtain a quick estimate of fit and eliminate
poor fitting respirators before going on to per-
form a full QNFT.
(3) A reasonably stable test agent concentration
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testing. For canopy or shower curtain types of
test units, the determination of the test agent’s
stability may be established after the test sub-
ject has entered the test environment.
(4) Immediately after the subject enters the test
chamber, the test agent concentration inside
the respirator shall be measured to ensure that
the peak penetration does not exceed 5 percent
for a half mask or 1 percent for a full facepiece
respirator.
(5) A stable test agent concentration shall be
(6) Respirator restraining straps shall not be
over-tightened for testing. The straps shall be
adjusted by the wearer without assistance
from other persons to give a reasonably
comfortable fit typical of normal use. The
respirator shall not be adjusted once the fit test
exercises begin.
(7) The test shall be terminated whenever any
single peak penetration exceeds 5 percent for
half masks and 1 percent for full facepiece res-
pirators. The test subject shall be refitted and
retested.
(8) Calculation of fit factors.
(i) The fit factor shall be determined for the
quantitative fit test by taking the ratio of the
average chamber concentration to the concen-
tration measured inside the respirator for each
test exercise except the grimace exercise.
(ii) The average test chamber concentration
shall be calculated as the arithmetic average of
the concentration measured before and after
each test (i.e., 7 exercises) or the arithmetic av-
erage of the concentration measured before
and after each exercise or the true average
measured continuously during the respirator
sample.
(iii) The concentration of the challenge agent
inside the respirator shall be determined by