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The Science of Fit and Fit Testing PPE for Worker Safety


Safety from work environment hazards is paramount. Proper fit – and fit testing – is an important part of your organization’s safety efforts. Fit testing is the process of determining whether a piece of PPE fits to provide the best possible level of hazard protection. While some types of PPE, such as tight-fitting respirators, have clearly documented processes to test for proper fit, testing for some types of equipment isn’t as prescriptive.

Stacy Richardson, a Senior Health and Safety Application Professional at 3M, helps outline some of the trends in fit testing and things to watch for when fit testing common types of PPE.

What Is PPE Compatibility?

The objective of PPE compatibility is to ensure effectiveness when multiple pieces must be worn at the same time. For example, a worker who needs to wear a respirator with prescription safety eyewear should be fit tested wearing both pieces of equipment to make sure they work effectively together. If the eyewear isn’t compatible with the respirator, and doesn’t sit properly on the face, the user may have obstructed vision, causing another potential safety hazard.

Compatibility also refers to instances where safety equipment is used alongside other types of equipment needed on the job. For example, if a worker needs a harness for fall protection, it must fit well with the tool belt they use every day, or any other equipment they need to do their job.

“You’re going to see manufacturers address PPE compatibility more in the future because the reality is if you’re wearing eyewear, you probably at some point are going to need to wear hearing protection or a respirator or a face shield or a harness,” Richardson said. “Different models will work better with others.”

Compatibility and Comfort

Another important aspect of compatibility is comfort. Uncomfortable safety equipment will likely be worn improperly or worse, not at all. Workers should be instructed to speak up if any of their safety equipment is uncomfortable, and that they should never just accept discomfort. If something doesn’t feel right, there’s probably a better option.

Since there are so many types of safety equipment to choose from, it may take some experimentation to find the perfect combination for everyone. There are many factors that can impact compatible fit, including head size and face shape, or if someone has recently experienced any physical changes such as weight loss or gain. Compatibility can be achieved by finding the right combination of PPE that fits, works well together, is comfortable and doesn’t interfere with any other equipment workers need to do their jobs.

There are reliable methods to test proper fit for hearing protection, safety eyewear, fall protection and head protection. Here’s a brief overview of methods used for these types of PPE.


In work environments where there are chemicals, dust or any kind of particulate in the air, it’s essential for employees to be protected and have continuous access to clean air. Properly fitting respirators can help protect lungs from hazardous chemicals, sprays and dust. OSHA requires fit testing annually – at minimum – for anyone required to wear a tight-fitting respirator in their work environment.

Quantitative vs. Qualitative Fit Testing

There are different methods of fit testing depending on the safety equipment. The terms quantitative and qualitative are typically used to refer to fit testing for respiratory equipment.

Quantitative fit testing is an objective method that can be used for any tight fitting face piece. One type of quantitative method measures the concentration of particulate matter both inside and outside the respirator. During this process, the employee is directed to go through a series of exercises. After each exercise, the machine provides feedback as a ratio called a fit factor.

“Each level of respiratory protection,” Richardson said, “has what we call a fit factor when you’re doing a quantitative fit test and you have to reach that fit factor to be considered a pass.”

A qualitative fit test is a subjective pass/fail test that relies on the wearer’s sense of taste and smell to know if there’s a break in the seal of their respirator. A common approved method uses a bitter or sweet challenge agent, either Bitrex or saccharin. The tester first sprays the agent using a nebulizer directly into the front of a hood into the persons breathing zone to first ensure they can detect the taste. Then the employee dons the respirator and completes a series of exercises while the tester spays the solution into the hood at a specific frequency. If the wearer cannot taste the solution while completing all required exercises, they pass the test. On the other hand, if they can detect the agent at all they may need to try a different respirator.

Richardson said: “Qualitative is subjective, so it’s really relying on somebody’s ability to sense, whether that’s taste or smell or an irritation to know if they have a break in their seal and it’s not fitting.”

What Are Fit Checks?

Fit checks can be performed by workers themselves prior to entering any contaminated area to ensure their face piece has a tight seal. Also called a user seal check, the user dons the equipment and then uses positive or negative pressure (sucking air in or blowing air out) to test the seal.

“For certain types of respirators, it’s just covering the inlets and breathing in deeply to make sure there's enough suction and then covering the exhalation valve and breathing out so you know you have a good seal,” Richardson said. “If you try it and it’s not sealing, that’s your indication that something’s not right. It could be missing a valve, a gasket, or it could be just worn out completely.”

Fit checks should never be used as an alternative for a fit test and should only be relied on for respiratory equipment that has already been fully fit tested. The primary difference between a fit check and a fit test is that fit checks are the employee’s responsibility, while fit tests are the employer’s responsibility.

Hearing Protection

Fit testing for hearing protection can also be done using both quantitative and qualitative methods. Quantitative testing revolves around two numbers, the noise reduction rating (NRR) and the personal attenuation rating (PAR).

Manufacturers set an NRR for each hearing protection product based on testing a group of people. The 3M earfit system is a quantitative test used to detect how much noise is getting behind a hearing protection device for a specific person. The value generated from this testing is the Personal Attenuation Rating (PAR). While the NRR number tells you what level of protection the product is rated to deliver, the PAR number provides a more exact measurement based on the individual wearing the equipment.

“When you get fit tested with hearing protection and you know it’s fitting,” Richardson said, “then you know, ‘OK, this is what it feels like when it’s fitting.’ So then, when you go out into the field to do it again, you’re like, ‘Oh, yep, I got that same feeling. I can tell it’s in there properly.’”

Once the user knows how their hearing protection should fit, whether it’s earmuffs, noise-reducing headsets or ear plugs, it will be easier for them to do their own qualitative testing based on fit. Another consideration is knowing when this type of protection needs to be replaced. Obvious signs of wear and tear are a tip-off that it might be time to either switch out parts of the hearing protection or replace it altogether.

“For earmuffs,” Richardson says, “the oils in your skin will break down the soft cushion that goes around your ear and make it hard and cracked, a definite sign you need to change it. There are also hygiene kits for earmuffs and it’s important to change out those seals so it’s always providing the best protection it can.”

Safety Eyewear

Fit testing for safety eyewear involves checking between the eyewear and specific gap points between the eyewear and the face. Having fit evaluation guidelines can help walk wearers through a fitting process. Part of the evaluation includes checking to make sure the user can see well in all directions and that the eyewear doesn’t obstruct visibility. Eyewear should also stay securely in place when the user moves their head in any direction. It’s also important that the eyewear is comfortable. The temple pieces should fit snugly but shouldn’t be too tight, and nose pieces should come in complete contact with the nose without pinching.

Richardson described part of the process 3M uses: “We go around the eye and see if there’s too much space and make sure that you have enough coverage. There are little gap gauges to make sure that the eyewear is fitting properly for your application.”

Fall Protection

When working at elevated heights, OSHA requires workers to wear a fall protection harness. In the event of a fall, the right safety harness will spread the shock of the fall across the user’s body and will keep them in an upright position. Fit testing fall protection starts with user size. Most manufacturers, Richardson said, have detailed sizing charts so users understand how and where a harness should fit them the best.

“A lot of people wear harnesses too loosely,” Richardson said. “And then, should a fall occur, it’s not going to protect you the way you need it to. It’s super important.”

Once users have been fit tested for the proper fall protection, it’s equally important to inspect these devices regularly for any damage. These inspections should be both visual and manual and should include looking for any damage to the webbing, stitching or hardware. Safety harnesses should also be cleaned regularly and stored in a clean, dry environment away from extreme temperatures or any corrosive agents. This handy inspection sheet from 3M covers the steps of a proper harness inspection. 

“When it comes to fall protection, it’s really about understanding how your harness needs to fit and where it needs to sit on the body,” Richardson said. “That’s really important in terms of making sure that it’s going to work properly when you need it to.”

Head Protection

The OSHA regulations for head protection are referenced in 1910.135 for general requirements and 1926.100 for construction. OSHA doesn’t specifically state which occupations or applications require hard hats; however, it does list some examples for whom this type of PPE should be considered, including carpenters, electricians, linemen, mechanics and plumbers.

Fit-Checking Head Protection

It’s important to make sure head protection is snug and secure and fits comfortably. There’s a variety of different hard hat and helmet manufacturers and models available, and most can be adjusted to the user’s unique head shape and size. The head protection should fit with a little space between its shell and internal suspension mechanism. The wearer should start by using a tape measure to get the circumference of their head. Then they should take the time to adjust the hard hat using the internal mechanism for their unique preferences. Comfort is key here because if a hard hat is required on a job site, it may be needed for extended periods. As with all safety equipment, if it’s not comfortable and therefore not worn properly, it can’t do its job.

When a workplace environment cannot be changed to eliminate potential hazards, PPE is needed.  Once it's determined PPE is needed, and the right equipment has been chosen, regular fit testing and fit checks can help offer a peace of mind that while on the job, workers are protected.

"If there is a way to fit test, that's ideal because then you've done your due diligence as a company, and as a health and safety person to do everything you can to make sure the equipment is fitting properly," Richardson said. "You can't control them after they leave work, but at least they're doing the right thing.” 

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The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.