Page 117 - L:\GROUP\SDT\zip_disk\Book2.PDF

the respirator and permits the wearer to make respirator performance in this Appendix.
certain the respirator is comfortable. This indi-
vidual shall already have been trained on how
to wear the respirator properly.
(3) Check the following conditions for the ad-
equacy of the respirator fit: Chin properly
placed; Adequate strap tension, not overly
tightened; Fit across nose bridge; Respirator of
proper size to span distance from nose to chin;
Tendency of the respirator to slip; Self-observa-
tion in a mirror to evaluate fit and respirator
position.
(4) Have the person wearing the respirator do
a user seal check. If leakage is detected, deter-
mine the cause. If leakage is from a poorly fit-
ting facepiece, try another size of the same
model respirator, or another model of respira-
tor.
(5) Follow the manufacturer’s instructions for
operating the Portacount and proceed with the
test.
(6) The test subject shall be instructed to per-
form the exercises in section I. A. 14. of this ap- that is required to hold the pressure in the
pendix.
(7) After the test exercises, the test subject shall pirator. The CNP fit test method measures
be questioned by the test conductor regarding
the comfort of the respirator upon completion
of the protocol. If it has become unacceptable,
another model of respirator shall be tried.
(b) Portacount Test Instrument.
(1) The Portacount will automatically stop and
calculate the overall fit factor for the entire set and holds his/her breath, after which an air
of exercises. The overall fit factor is what
counts. The Pass or Fail message will indicate
whether or not the test was successful. If the
test was a Pass, the fit test is over.
(2) Since the pass or fail criterion of the
Portacount is user programmable, the test op-
erator shall ensure that the pass or fail crite-
rion meet the requirements for minimum
109
(3) A record of the test needs to be kept on file,
assuming the fit test was successful. The
record must contain the test subject’s name;
overall fit factor; make, model, style, and size
of respirator used; and date tested.
4. Controlled negative pressure (CNP) quanti-
tative fit testing protocol.
The CNP protocol provides an alternative to
aerosol fit test methods. The CNP fit test
method technology is based on exhausting air
from a temporarily sealed respirator facepiece
to generate and then maintain a constant
negative pressure inside the facepiece. The
rate of air exhaust is controlled so that a con-
stant negative pressure is maintained in the
respirator during the fit test. The level of pres-
sure is selected to replicate the mean inspira-
tory pressure that causes leakage into the
respirator under normal use conditions. With
pressure held constant, air flow out of the res-
pirator is equal to air flow into the respirator.
Therefore, measurement of the exhaust stream
temporarily sealed respirator constant yields a
direct measure of leakage air flow into the res-
leak rates through the facepiece as a method
for determining the facepiece fit for negative
pressure respirators. The CNP instrument
manufacturer Dynatech Nevada also provides
attachments (sampling manifolds) that replace
the filter cartridges to permit fit testing in an
employee’s own respirator. To perform the
test, the test subject closes his or her mouth
pump removes air from the respirator
facepiece at a pre-selected constant pressure.
The facepiece fit is expressed as the leak rate
through the facepiece, expressed as milliliters
per minute. The quality and validity of the
CNP fit tests are determined by the degree to
which the in-mask pressure tracks the test
pressure during the system measurement time
of approximately five seconds. Instantaneous