3M Respirator Seal Check

Importance of a User Seal Check

The simple habit that helps put you in control of your respiratory protection

ST. PAUL, Minn. – You’ve put on your respirator and other safety equipment. It’s time to get to work. You know your employer chose appropriate equipment for your job, and you passed your annual respirator fit testing. So you’re good to go, right?

Not until you perform one easy task that should be an ingrained habit every time you use a respirator: a user seal check.

A user seal check is a quick (and required) way to help you ensure your respirator is sealing correctly when you’re on the job — without any special equipment needed.

So if you haven’t already, start to make user seal checks a daily habit entering contaminated areas – and if you’re in charge of others, make sure they’re doing them too.

Positive or negative pressure?

There are two basic methods for performing a user seal check: positive pressure and negative pressure. As long as they’re performed according to the user instructions specific to your respirator, both are considered effective tests of the seal by OSHA.

  • Positive pressure means you test the seal by exhaling while covering the respirator on filtering facepiece respirators or exhalation valve on certain other elastomeric respirators. 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.


  • Negative pressure involves inhaling while covering the respirator on filtering facepiece respirators or, the filters or cartridges on elastomeric respirators. 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.

(Note that on disposable respirators, the exhalation valves are not designed for positive pressure user seal checks. If you wear a valved disposable respirator, you must conduct a negative pressure user seal check.)

Seal check vs. fit test: What’s the difference?

Studies have shown that user seal checks tend to improve the fit of respirators.1 But this procedure is not a replacement for respirator fit testing, which must occur at least annually. Both practices are required by OSHA2 and by similar regulations in many other countries, and both contribute to the effectiveness of respiratory protection.

Before wearing any respirator in a contaminated area, a qualitative or quantitative fit test must be performed to confirm that the respirator fits and can protect against contaminants. That said, once you have a fit-tested respirator, user seal checks are also required to help you ensure that you have an adequate seal every time you put the respirator on.

For more information on a user seal check, visit our 3M Center for Respiratory Protection.


  1. Myers, W.R., M. Jaraiedi, and L. Hendricks. 1995. Effectiveness of fit check methods on half mask respirators. Applied Occupational and Environmental Hygiene. 10 (11): 934-942.Viscusi, D.J., M.S. Bergman, Z. Zhuang, and R.E. Shaffer. 2012. Evaluation of the benefit of the user seal check on N95 filtering facepiece respirator fit. Journal of Occupational and Environmental Hygiene. 9 (6): 408-16.
  2. Occupational Safety & Health Administration (OSHA) Respiratory Protection Standard (29 CFR 1910.134). Appendix A: Fit Testing Procedures (Mandatory); Appendix B-1: User Seal Check Procedures (Mandatory)