How do you seal check a respirator?

Short answer: To seal check a respirator, perform a positive pressure check by covering the exhalation valve and exhaling gently so the facepiece bulges slightly without air escaping, then a negative pressure check by covering the cartridges or inlets and inhaling so the facepiece collapses inward and stays collapsed. A correct user seal check is required by OSHA 1910.134 Appendix B-1 every single time you don a tight-fitting respirator. If air leaks at either step, reseat the mask and adjust the straps until both checks hold.

How to seal check a respirator: user seal checks explained (2026)

Learning how to seal check a respirator is the single habit that decides whether your mask actually protects you on a given shift, because a respirator that is not sealed to your skin leaks contaminated air around the edges no matter how good the filter is. The federal standard that governs tight-fitting respirators, OSHA 29 CFR 1910.134, requires a user seal check every time the respirator is donned, using the procedures spelled out in its Appendix B-1. This guide is written for workers, safety managers, and supervisors who want the seal check to be quick, repeatable, and correct under real conditions.

Below we break down the two seal check methods - positive pressure and negative pressure - explain exactly what a passing result looks like, and clarify the difference between a seal check and a formal fit test. We then walk through the check on a real half mask respirator so the workflow is concrete, and connect it to the rest of your respiratory program, including the annual fit testing that the seal check does not replace.

Why this matters.
A respirator that passes a seal check at the start of every donning is the difference between the assigned protection factor on paper and real exposure to dusts, vapors, or pathogens. OSHA 1910.134(g)(1)(iii) makes the user seal check mandatory on each use, and a tight-fitting half mask has an assigned protection factor of only 10 - meaning a sealed mask cuts exposure to one-tenth, while a leaking one offers little real protection. Skipping the check, or wearing the mask over facial hair that breaks the seal, voids that protection and the compliance of the whole program.

Part 1 - What a user seal check actually is

A user seal check is a quick self-test the wearer performs to confirm that a tight-fitting respirator is seated and sealed against the face at the moment of donning. It is not a measurement of protection level - it is a go/no-go check that catches an obviously bad seal before you enter the hazard area. OSHA 1910.134 Appendix B-1 recognizes two acceptable methods: the positive pressure check and the negative pressure check.

• Who must do it: every wearer of a tight-fitting respirator - half mask, full facepiece, or elastomeric - each and every time the unit is put on.
• When: after donning and adjusting straps, before entering the contaminated atmosphere, and again any time the mask is repositioned.
• What it cannot do: a seal check does not quantify fit, does not replace fit testing, and is not valid on a loose-fitting hood or a poorly maintained mask.

The seal check works only on a respirator that has already passed a formal fit test in that exact make, model, and size - the check confirms the known-good seal is achieved today.

Part 2 - The positive pressure seal check

The positive pressure check verifies the seal by trapping exhaled air inside the mask. After donning and adjusting the straps:

• Cover the exhalation valve with your palm. On most half masks this is the round port at the bottom front of the facepiece.
• Exhale gently and steadily. Do not blow hard.
• A good seal makes the facepiece bulge slightly outward and hold positive pressure with no air felt escaping around the edges, nose, or chin.

If you feel air leaking at the nose bridge, cheeks, or jaw, the seal has failed. Reposition the mask, retension the straps from the bottom up, and repeat. The positive pressure method is the appropriate check for any respirator that has an accessible exhalation valve to cover, such as the units in our half mask respirators lineup.

Part 3 - The negative pressure seal check

The negative pressure check verifies the seal by creating a vacuum inside the mask. After donning:

• Cover the air inlets - the cartridges or filters - with your palms, or cap them per the manufacturer's instructions. On a cartridge respirator that means blocking both filters or cartridges.
• Inhale gently so the facepiece collapses slightly toward your face.
• Hold your breath for about 10 seconds. A good seal keeps the facepiece collapsed with no inward leakage; if it springs back or you feel air drawn in around the edges, the seal has failed.

The negative pressure check is the right method for filtering facepieces and cartridge respirators where the inlets can be blocked. Many wearers run both checks back to back for confidence. If either check fails repeatedly, the problem is fit, facial hair, or a worn part - see our guide on what happens when a respirator does not fit.

Part 4 - Why a seal check is NOT a fit test

This is the most common and most dangerous misconception in respiratory protection. A user seal check and a fit test are different procedures with different purposes:

• A seal check is a quick, subjective, qualitative self-test done by the wearer at every donning to confirm the mask is seated. It produces a yes or no.
• A fit test is a formal, supervised procedure done at least annually (and at initial assignment) that verifies a specific make, model, and size of respirator fits that individual's face well enough to achieve protection. It produces a documented pass with a fit factor.

Passing a seal check tells you the mask is sealed right now; it tells you nothing about whether that model was ever proven to fit your face. You must do both. The annual requirement and protocols are covered in our respirator fit testing guide, and the legal basis is OSHA 1910.134(f) for fit testing and (g)(1)(iii) for seal checks.

Part 5 - When to seal check a respirator, and what defeats it

Run a user seal check every time you don a tight-fitting respirator - at the start of the shift, after every break, and any time the mask is removed or repositioned. There is no number of skips that is acceptable; the standard says each use.

What defeats a seal check

• Facial hair in the seal area. Even a day or two of stubble breaks the seal - see respirators and beards for the OSHA rule.
• Wrong size or model that was never fit tested on your face.
• Worn straps, cracked facepiece, or a missing exhalation valve disc - inspect before use per our maintenance and inspection guide.
• Eyeglass temples or PPE crossing the seal on a full facepiece.

If the mask will not pass after reseating, do not enter the hazard - swap to a different size or a fit-tested alternative from our respiratory protection range.

Part 6 - Seal checks on half masks vs full facepieces

The two seal check methods apply across respirator types, but the practical details differ.

• Half masks seal across the nose bridge, cheeks, and under the chin. The exhalation valve is easy to cover for a positive check, and the cartridges are easy to block for a negative check. A correctly sealed half mask earns its assigned protection factor of 10.
• Full facepiece respirators seal at the forehead, temples, and jaw and cover the eyes. They achieve a higher assigned protection factor (up to 50 in negative pressure mode) and are common in our full face mask respirators collection. Eyeglasses must use a manufacturer spectacle kit so the temples do not break the seal.

For both types, the seal check only confirms a fit that was established by the annual fit test, and both require a medical evaluation before use under OSHA 1910.134(e).

Positive vs negative pressure user seal checks (OSHA 1910.134 Appendix B-1)

Part 7 - Worked example: seal check a respirator (3M half mask)

To make the workflow concrete, here is how to seal check a respirator using a cartridge half mask such as the 3M 7500 Series half mask respirator fitted with a pair of 3M 2091 P100 filters. Confirm the mask is the make, model, and size you were fit tested in before you start.

1. Inspect and don the respirator. Check the facepiece, straps, and exhalation valve disc for damage, then place the mask over your nose and mouth and pull the head harness over the crown of your head.
2. Tension the straps from the bottom up. Snug the lower (neck) straps first, then the upper (head) straps. The mask should sit firmly without painful pressure points, with no gaps at the nose bridge or chin.
3. Run the positive pressure check. Cover the exhalation valve at the front of the facepiece with your palm and exhale gently. The mask should bulge slightly and hold pressure with no air escaping around the edges. If you feel a leak, reseat and retension.
4. Run the negative pressure check. Cover both P100 filters with your palms and inhale gently. The facepiece should collapse toward your face and stay collapsed for about 10 seconds with no inward leakage.
5. Reseat and repeat if either check fails. If air leaks at the nose, cheeks, or chin, reposition the mask, retension the straps from the bottom up, and run both checks again. Do not enter the hazard until both hold.
6. Document and proceed. Once both checks pass, you are sealed for this donning. Repeat the full check after every break or any time the mask is moved, and remember the seal check does not replace your annual fit test or medical evaluation.

The same two-step routine applies to every tight-fitting mask we stock, from a 3M 6000 Series half mask to a Honeywell North 5500 Series half mask. For the steps that come before and after the seal check, see how to put on and take off a respirator and our fit testing guide.

Frequently asked questions

How do you seal check a respirator?

Run two checks after donning. For the positive pressure check, cover the exhalation valve and exhale gently so the facepiece bulges and holds pressure. For the negative pressure check, cover the cartridges and inhale gently so the facepiece collapses and stays collapsed. If air leaks at either step, reseat and retension the straps. OSHA 1910.134 Appendix B-1 defines both methods.

What is the difference between a positive and negative pressure seal check?

A positive pressure check covers the exhalation valve and uses a gentle exhale to pressurize the mask; a passing seal makes it bulge without leaking. A negative pressure check covers the filter inlets and uses a gentle inhale to create a vacuum; a passing seal makes the facepiece collapse and stay collapsed. Both confirm the seal, and many wearers run both each time they seal check a respirator.

Is a user seal check the same as a fit test?

No. A seal check is a quick self-test done at every donning to confirm the mask is seated; a fit test is a formal, supervised procedure done at least annually to prove a specific model and size fits your face. A seal check never replaces a fit test - see our respirator fit testing guide for the annual requirement.

When do you need to seal check a respirator?

Every single time you put on a tight-fitting respirator - at the start of the shift, after every break, and any time the mask is removed or repositioned. OSHA 1910.134(g)(1)(iii) requires a user seal check on each use.

How do you seal check an N95 filtering facepiece?

Cup both hands over the whole respirator, exhale sharply, and feel for leakage at the edges - the mask should billow slightly. Then inhale sharply; the mask should draw in toward your face. If air leaks at the nose clip or edges, reposition and re-form the nose clip. Note that an N95 still requires fit testing, covered in N95 vs P100.

Why does my respirator fail the seal check?

The most common causes are facial hair in the seal area, the wrong size or model, worn straps or a cracked facepiece, or a missing exhalation valve disc. Reseat the mask and retension the straps from the bottom up; if it still fails, the unit needs inspection or a different size. See respirator maintenance and inspection.

Can you pass a seal check with a beard?

Reliably, no. Facial hair that crosses the sealing surface of a tight-fitting respirator prevents a consistent seal, which is why OSHA prohibits it on tight-fitting masks. Even passing a single seal check over stubble does not mean the seal holds through a shift; bearded workers should use a loose-fitting PAPR instead.

What does a passing positive pressure seal check feel like?

When you cover the exhalation valve and exhale gently, the facepiece pushes outward slightly and holds that pressure, and you feel no air escaping at the nose bridge, cheeks, or under the chin. If air whistles or puffs out at any edge, the seal has failed and you must reseat the mask.

How long should you hold a negative pressure seal check?

Cover the inlets, inhale gently, and hold for about 10 seconds. A good seal keeps the facepiece collapsed against your face for the full time. If it springs back or you feel air drawn in around the edges before the 10 seconds are up, the seal has failed.

Do you seal check a respirator before or after a fit test?

You seal check at every donning, including immediately before each fit test - the fit testing protocol itself begins with a successful user seal check. But the seal check is an ongoing daily step, while the fit test is a once-a-year (and at-assignment) procedure described in our fit testing guide.

Does a half mask need a different seal check than a full facepiece?

The two methods are the same, but the contact points differ. A half mask seals across the nose, cheeks, and chin; a full facepiece seals at the forehead, temples, and jaw. On a full facepiece, eyeglass temples must use a spectacle kit so they do not break the seal.

What assigned protection factor does a sealed half mask give?

A properly sealed, fit-tested tight-fitting half mask has an assigned protection factor of 10, meaning it reduces exposure to one-tenth of the ambient concentration. A leaking mask offers far less, which is exactly why the user seal check matters. Full facepieces reach up to 50; see N95 vs P100 for filter classes.

Can I just seal check a respirator instead of fit testing?

No, and treating them as interchangeable is a compliance violation. The seal check confirms today's donning; the fit test proves the model fits your face at all. OSHA 1910.134(f) mandates fit testing at assignment and annually regardless of how reliably you pass seal checks.

What should I inspect before a seal check?

Check the facepiece for cracks or distortion, the head straps for stretching or breaks, the exhalation valve and valve disc for tears or debris, and the cartridges or filters for damage and secure attachment. A damaged part will fail the seal check or, worse, let air leak undetected. See our maintenance and inspection guide.

Does the user seal check method come from OSHA or the manufacturer?

Both. OSHA 1910.134 Appendix B-1 sets the mandatory positive and negative pressure procedures, and you must also follow any equally effective check the manufacturer specifies for that model. The standard itself is explained in our OSHA 1910.134 guide.

What do I do if a respirator will not pass a seal check?

Do not enter the contaminated area. Reseat the mask and retension the straps; if it still leaks, try a different size or a model that was fit tested on your face from our respiratory protection range. A persistent failure usually means wrong fit, facial hair, or a worn component, not user error.

Is a seal check required on a loose-fitting PAPR hood?

No. User seal checks apply only to tight-fitting respirators that seal to the skin. Loose-fitting powered air-purifying respirator hoods and helmets rely on positive airflow rather than a face seal, so they are not seal checked - though they have their own airflow checks. Browse options in powered air-purifying respirators.

Further reading on this site

• Respirator fit testing guide — the annual procedure that a seal check supplements but never replaces.
• How to put on and take off a respirator — the donning and doffing sequence that brackets every seal check.
• What happens if a respirator does not fit — seal failure, protection factor loss, and how to recognize a bad seal.
• Respirator maintenance and inspection — the pre-use checks that keep a respirator able to pass a seal check.
• Half mask respirators — tight-fitting half masks that require a positive and negative pressure seal check.
• Full face mask respirators — higher protection facepieces with the same two seal check methods.
• OSHA 1910.134 explained — the respiratory protection standard behind the seal check rule.
• Respirator medical evaluation — the 1910.134(e) clearance required before any tight-fitting respirator use.