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Appendix B-1 to 1910.134 user seal check
procedures

I. Facepiece Positive and/or Negative Pressure
Checks

A. Positive pressure check. Close off the
exhalation valve and exhale gently into the
facepiece. The face fit is considered satisfactory
if a slight positive pressure can be built up
inside the facepiece without any evidence of
outward leakage of air at the seal. For most
respirators this method of leak testing requires
the wearer to first remove the exhalation valve
cover before closing off the exhalation valve
and then carefully replacing it after the test.

B. Negative pressure check. Close off the inlet
opening of the canister or cartridge(s) by
covering with the palm of the hand(s) or by
replacing the filter seal(s), inhale gently so that
the facepiece collapses slightly, and hold the
breath for ten seconds. The design of the inlet
opening of some cartridges cannot be
effectively covered with the palm of the hand.
The test can be performed by covering the inlet
opening of the cartridge with a thin latex or
nitrile glove. If the facepiece remains in its
slightly collapsed condition and no inward
leakage of air is detected, the tightness of the
respirator is considered satisfactory.

II. Manufacturer’s Recommended User Seal Check
Procedures

The respirator manufacturer’s recommended
procedures for performing a user seal check
may be used instead of the positive and/or
negative pressure check procedures provided
that the employer demonstrates that the
manufacturer’s procedures are equally
effective.

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