Appendix B: Positive and Negative-Pressure User Seal Checks – Elastomeric Facepiece Respirators

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Part 1: Negative Pressure User Seal Check
  • Close off the inlet openings of the tight-fitting elastomeric facepiece respirator (where the filters are attached to the respirator) using your hands or nonpermeable, flexible plastic wrap.
  • Inhale gently and hold your breath for at least 5 seconds. Do not attempt to adjust the facepiece while under negative pressure.
  • The user seal check is successful if the facepiece remains slightly collapsed while the breath is held.
  • If the facepiece does not remain collapsed, verify that nothing is obstructing the seal, adjust the facepiece and harness and repeat the user seal check.
  • If the facepiece still does not remain collapsed, remove the respirator, inspect the components for the cause of the leakage, correct any problems discovered or obtain a replacement respirator and repeat the user seal check.
Part 2: Positive Pressure User Seal Check
  • Close off the exhalation valve with your hand.
  • Exhale gently. Do not disturb the facepiece while sealing off the exhalation valve.
  • The user seal check is successful if a slight positive pressure can be maintained inside the facepiece and you cannot detect any outward leakage of air.
  • If a slight positive pressure cannot be maintained inside the facepiece for 5 seconds, verify that nothing is obstructing the seal, adjust the facepiece and harness and repeat the user seal check.
  • If a slight positive pressure still cannot be maintained inside the facepiece, remove the respirator, inspect the components for the cause of the leakage, correct any problems discovered or obtain a replacement respirator and repeat the user seal check