Filtering out Confusion: 

Frequently Asked Questions about Respiratory Protection

User Seal Check

Over 3 million United States employees in approximately 1.3 

million workplaces are required to wear respiratory protection. 

The Occupational Safety and Health Administration (OSHA) 

(29 CFR 1910.134) requires an annual fit test to confirm the 

fit of any respirator that forms a tight seal on the wearer’s face 

before it is used in the workplace.1 Once a fit test has been done 

to determine the best respirator model and size for a particular 

user, a user seal check should be done every time the respirator 

is to be worn to ensure an adequate seal is achieved.

What is a User Seal Check?

A user seal check is a procedure conducted by the respirator wearer to determine if the respirator is being properly worn. The user seal check can either be a positive pressure or negative pressure check. 

During a positive pressure user seal check, the respirator user exhales gently while blocking the paths for air to 

exit the facepiece. A successful check is when the facepiece is slightly pressurized before increased pressure causes 

outward leakage. 

During a negative pressure user seal check, the respirator user inhales sharply while blocking the paths for air to 

enter the facepiece. A successful check is when the facepiece collapses slightly under the negative pressure that is 

created with this procedure. 

A user seal check is sometimes referred to as a fit check. A user seal check should be completed each time the 

respirator is donned (put on). It is only applicable when a respirator has already been successfully fit tested on the 

individual.

How do I do a User Seal Check while Wearing a Filtering Facepiece 

Respirator?

Not every respirator can be checked using both positive and negative pressure. Refer to the manufacturer’s instructions for conducting user seal checks on any specific respirator. This information can be found on the box or 

individual respirator packaging. 

The following positive and negative user seal check procedures for filtering facepiece respirators are provided as 

examples of how to perform these procedures.
This document is in the public domain

and may be freely copied or reprinted.

DOI: https://doi.org/10.26616/NIOSHPUB2018130

DHHS (NIOSH) Publication No. 2018-130

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How to do a positive pressure user seal check

Once the particulate respirator is properly donned, place your hands over the facepiece, covering as much surface 

area as possible. Exhale gently into the facepiece. The face fit is considered satisfactory if a slight positive pressure 

is being built up inside the facepiece without any evidence of outward leakage of air at the seal. Examples of such 

evidence would be the feeling of air movement on your face along the seal of the facepiece, fogging of your glasses, or a lack of pressure being built up inside the facepiece.

If the particulate respirator has an exhalation valve, then performing a positive pressure check may be impossible. 

In such cases, a negative pressure check should be performed.

How to do a negative pressure user seal check 

Negative pressure seal checks are typically conducted on particulate 

respirators that have exhalation valves. To conduct a negative pressure 

user seal check, cover the filter surface with your hands as much as possible and then inhale. The facepiece should collapse on your face and 

you should not feel air passing between your face and the facepiece.

In the case of either type of seal check, if air leaks around the nose, use 

both hands to readjust the nosepiece by placing your fingertips at the 

top of the metal nose clip. Slide your fingertips down both sides of the 

metal strip to more efficiently mold the nose area to the shape of your 

nose. Readjust the straps along the sides of your head until a proper 

seal is achieved.2

If you cannot achieve a proper seal due to air leakage, you may need to 

be fit tested for a different respirator model or size. 

 

Can a user seal check be considered a substitute for a fit testing? 

No. The user seal check does not have the sensitivity and specificity to replace either fit test methods, qualitative 

or quantitative, that are accepted by OSHA (29 CFR 1910.134). A user should only wear respirator models with 

which they have achieved a successful fit test within the last year. NIOSH data suggests that the added care from 

performing a user seal check leads to higher quality donnings (e.g., reduces the chances of a donning with a poor 

fit).3

Where can I Find More Information? 

This information and more is available on the NIOSH Respirator Trusted-Source webpage.

References

1. OSHA [1998]. Respiratory Protection. 29 CFR 1910.134. Final rule. Fed Regist 63:1152-1300.

2. NIOSH [2010]. How to properly put on and take off a disposable respirator. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Insitute for 

 Occupational Safety and Health, DHHS (NIOSH) Publication No. 2010-133 https://www.cdc.gov/niosh/docs/2010-133/pdfs/2010-133.pdf 

3. Viscusi DJ, Bergman MS, Zhuang Z, and Shaffer RE [2012]. Evaluation of the benefits of the user seal check on N95 filtering facepiece respirator fit. J Occup and Evironl Hyg. 9(6):408-416.

Photos courtesy of NIOSH