Industrial and Lab Safety: Checking the Fit of Your Respirator


To maintain lab safety or adequate protection in the manufacturing facility or field, the fit of your respirator is important. When wearing a tight-fitting respirator, perform a user seal check to ensure that an adequate seal is achieved each time the respirator is put on.

User Seal Check Procedure

North Full-Face Respirator, Thermoplastic Elastomer

North Full-Face Respirator, Thermoplastic Elastomer

Follow either the positive and negative pressure checks listed below or the manufacturer’s recommended user seal check method. User seal checks are not substitutes for qualitative or quantitative fit tests.

Facepiece Positive and/or Negative Pressure Checks

Positive Pressure Check. Close off the exhalation valve and exhale gently into the facepiece. Face fit is considered satisfactory if 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.

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 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 a slightly collapsed condition and no inward leakage of air is detected, the tightness of the respirator is considered satisfactory.

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.

Qualitative vs. Quantitative Fit Testing

Qualitative Fit Testing (QLFT) may be used to fit test negative pressure air-purifying respirators if they will only be used in atmospheres less than ten times the permissible exposure limit (PEL). Existing evidence only validates current QLFT protocols to identify respirators that achieve a fit factor of 100 or less.

Quantitative Fit Testing (QNFT) must be used if respirators are to be used in atmospheres with substance concentrations greater than ten times the PEL. When QNFT is used, all full facepiece respirators must meet or exceed a fit factor of 500, while quarter- and half-mask respirators must meet or exceed 100. 

See all respirators.

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