How to Do a User Seal Check Every Time

Why this matters

A tight-fitting respirator protects exactly as well as its seal. A half-mask with a gap at the nose bridge pulls unfiltered air through the gap, because the gap is the easiest path, and the filter rated to stop 99.97 percent of particles ends up filtering the share of air that bothered to go through it. The annual fit test proved the mask can seal on that face. The user seal check, done every time the mask goes on, proves it sealed this morning. It takes under a minute, and it is the step people drop first.

What the seal check is, and what it is not

Under 29 CFR 1910.134(g)(1)(iii), an employee wearing a tight-fitting respirator performs a user seal check each time the respirator is put on, using the procedures in Appendix B-1 of the standard or the manufacturer's procedure if it is equally effective. Construction work reaches the same requirement through 29 CFR 1926.103, which applies 1910.134.

The fit test and the seal check answer different questions, and neither replaces the other.

• The fit test (29 CFR 1910.134(f), before first use, at least annually, and when something about the face changes) measures leakage with test agents or instruments and establishes that this make, model and size can seal on this person. It is a qualifying measurement. See related: OSHA Respiratory Protection - Annual Fit Test.
• The seal check is a crude, self-administered test of whether the mask is sealed right now. It catches a strap set wrong, a mask riding high, a dirty or curled valve flap, a missing cartridge gasket. It cannot detect a small chronic leak, and a mask that passes the seal check can still fail a fit test. A pass means "no gross leak today," never "fit tested."

It applies to tight-fitting facepieces: filtering facepieces (the disposable dust mask style), elastomeric half-masks and full-face masks. A loose-fitting hood or helmet on a powered air-purifying respirator does not seal on the face and has no seal check; it has its own airflow check.

Where the seal leaks

The seal fails at the same few places on almost every face, and knowing them tells you where to feel and what to adjust.

        nose bridge: the most common leak.
        a mask riding high or a bent nose
        clip opens a gap here first
               \
           .----\---.
          /  __  \   \  <- cheek: gaps over a
         |  (  )      |    thin face or deep
   upper |   --       |    cheek hollow
   strap |   [valve]  |
   above |            |  <- side of chin and
   ears  \   ______   /    jaw: stubble and a
          \ /      \ /     mask set too low
           '--chin-'
               |
        lower strap behind the neck,
        below the ears

A leak you feel as air on the eyes is almost always the nose bridge. A leak along the jaw that changes when you open your mouth is the chin, and usually means the mask is too small or sitting too low.

Step 1: Inspect the respirator before it touches your face

Look over the facepiece for cracks, tears, distortion and stiffened rubber; flex the straps for lost elasticity; check that the inhalation and exhalation valve flaps are present, flat, clean and not curled; confirm each cartridge or filter is the right type, seated, and has its gasket. 29 CFR 1910.134(h)(3) requires inspection before each use for respirators used in routine situations. The reason: most seal-check failures are hardware, not technique. Skip it and a curled exhalation flap passes leakage you will spend five minutes trying to strap out.

Step 2: Make the face ready for a seal

Under 29 CFR 1910.134(g)(1)(i)(A), a tight-fitting respirator may not be worn by someone who has facial hair that comes between the sealing surface and the face or that interferes with valve function. That means the sealing zone in the diagram is clean-shaven on the day; a beard, a goatee that reaches the chin seal, or sideburns under the strap line all count. Glasses or goggles are worn so they do not interfere with the seal, which is (g)(1)(ii); a temple arm under a full-face seal does interfere. Skip it and no amount of strap adjustment will close the gap, and the seal check may still pass because hair fills the gap well enough to fool a crude test while leaking under work breathing.

Step 3: Put it on in the same order every time

Cup the mask over nose and chin, nose first, then pull the upper strap over the crown and the lower strap behind the neck below the ears. Tighten the lower straps first, then the upper, snug but not crushing; overtightening folds the seal and opens a gap at the side. For a disposable filtering facepiece, mold the nose clip with two fingers of each hand working outward from the center, never pinched with one hand, which kinks it into a point. The reason: order and symmetry are what make the seal repeatable. Skip it and the check passes one day and fails the next with nothing apparently different.

Step 4: Do the negative-pressure check

Close off the inlets: palms flat over both cartridges or filters, or the filter seals or covers the manufacturer provides. Inhale gently so the facepiece pulls in slightly against your face, then hold your breath for about 10 seconds, which is the interval Appendix B-1 gives. Pass: the facepiece stays slightly collapsed and you feel no air coming in at the edges. The reason: under negative pressure any gap draws air in, and the collapse holding is the evidence there is no gap. Skip it and you have no test of the inhalation side, which is the side the contaminant enters on. Some cartridges are shaped so your palms cannot close them; there, the manufacturer's procedure governs.

Step 5: Do the positive-pressure check

Close off the exhalation valve with your palm, or on masks where the valve cover must come off to do this, remove it and replace it after. Exhale gently. Pass: a slight positive pressure builds inside the facepiece with no air escaping at the seal. The reason: it tests the seal from the other direction and checks that the exhalation valve is closing. Skip it and a valve that sticks open, which lets unfiltered air in on every breath, goes unnoticed.

For a disposable filtering facepiece the manufacturer's check is different: cover the front with both hands and exhale sharply on an unvalved mask, or inhale sharply on a valved one, feeling for air at the edges.

Step 6: Read a failure, fix one thing, and recheck

A failed check is information about where, not just whether.

• Air on the eyes or at the nose: reseat the mask lower on the nose, reshape the nose clip, recheck.
• Air at the cheeks or jaw: loosen and re-tension the lower straps evenly, recheck.
• The collapse releases with no leak you can feel: suspect hardware, a cartridge gasket missing or an inhalation valve flap lifting. Go back to step 1.
• Positive check vents through the valve: the exhalation flap is dirty, curled or missing. Clean or replace it.

Change one thing at a time and recheck after each, so you know what fixed it. The stop rule: if two adjustments do not produce a pass, the respirator does not go into the work area. Swap the respirator or the part, recheck, and if it still fails, do not do the task; tell your supervisor, because a mask that used to pass and no longer does may mean a changed face, a wrong size or a damaged facepiece. Weight change, dental work and facial scarring are among the changes that call for a new fit test under 1910.134(f).

Worked example: two techs, one gate

A shop's respiratory protection program assigns half-mask elastomeric respirators with P100 filters for a dusty demolition task. Two techs are suiting up at the truck.

The first tech is clean-shaven and fit tested four months ago on a medium. Inspection passes. On the negative check he holds his breath and the facepiece relaxes after about 4 seconds, short of the 10, with a faint draw of air felt at the bridge of the nose. That is a fail. He reseats the mask a little lower and remolds nothing (an elastomeric half-mask has no clip), then rechecks: it holds for the full 10 seconds with no air felt. The positive check builds pressure with nothing escaping at the seal. Pass, one adjustment, and he goes to work.

The second tech has a short beard. His mask was fit tested last year, before the beard. The check is not even attempted, because step 2 already failed: hair under the sealing surface is excluded by 1910.134(g)(1)(i)(A) regardless of how the check would come out, and a pass through hair would be a false pass. The options are his to choose with the supervisor, and the respirator is not one of them today: shave and do the check, or move to a part of the job without the exposure, or use a respirator that does not depend on a face seal. The shop's program lists a powered air-purifying respirator with a loose-fitting hood as the alternative for exactly this case, because a loose-fitting hood has no facial-hair restriction. He takes the reassignment for the day.

What changes the answer. If the shop's program covered this task only as voluntary use of a filtering facepiece, the seal check would still be the right habit but not a requirement attached to that use, and the beard question would be one of effectiveness rather than compliance. Which tier the use falls in is not decided here; see related: Voluntary Respirator Use and What the Shop Still Owes.

References

• 29 CFR 1910.134(g)(1), (h)(3) and Appendix B-1, User Seal Check Procedures; 29 CFR 1926.103
• 29 CFR 1910.134(f), fit testing
• NIOSH respirator user notices and the respirator manufacturer's donning and seal check instructions
• See related: OSHA Respiratory Protection - Annual Fit Test
• See related: Voluntary Respirator Use and What the Shop Still Owes