Sensitivity Test for Mask Fitting: How to Administer a Respirator Fit Test

It's an employer's responsibility to fit test workers with the respirators used on their job sites. Most folks don't think about this unless they are in highly regulated fields. But under OSHA safety standard 1910.134 employers are required to show each worker using this lung protection equipment how to put on a respirator, how to position it on the face, and how to determine an acceptable fit. If you've never performed a fit test, here is a quick primer on how to use a Qualitative Fit Test Apparatus from 3M and Allegro.

The test is designed to make sure the wearer of the respirator can achieve an adequate seal between the unit and their face. It relies upon the ability of the wearer to detect the taste of either a bitter or a sweet solution when the test administrator injects the solution into the hood in the form of a fine mist. Both the sweet and the bitter kits may be required as some employees may simply not have the pallet sensitivity to recognize one or the other taste.

The 3M FT-30 Bitrex Fit Test Kit is a popular kit. It contains a hood, a plastic collar, a laminated instruction book (in both English and Spanish), a bitter-tasting sensitivity solution, two nebulizers, and two replacement nebulizer inserts. It comes in a cardboard carrying case. An identical kit is available from 3M with a sweet, saccharin test solution.

The tests are suitable for checking the fit of disposable respirators rated N95 or above or half-face reusable respirators with particulate or combination filters.

The 3M kits, as well as the Allegro Bitrex Respirator Fit Test Kit and the Allegro Saccharin Respirator Fit Test Kit contain similar equipment and the tests should be conducted in the same way.

The test itself breaks down into two parts: the sensitivity test, and the actual fit test. To administer the sensitivity test, open your bottle of Bitrex or Saccharin solution and the top of your nebulizer. Add approximately 1 teaspoon of the solution into the reservoir at the top of the bulb. Put the top of the nebulizer back on. Then, while squeezing the bulb several times look carefully to confirm the device is creating a mist. Next, make sure to ask the test subject if they have had anything to eat or drink except for water and that they have not chewed gum for at least 15 minutes prior to the test. If they have, wait an appropriate amount of time before beginning the test as lingering flavors in the test subject's mouth may affect their ability to recognize the test solution.

Place the hood and collar over the subject's head. For this first test the subject will not be wearing any type of respirator. The sensitivity test is to make sure the subject can taste and recognize the nebulized solution. Ask the subject to breathe through their mouth with their tongue slightly out. Have them indicate when they taste the solution by raising their hand.

Place the nebulizer valve through the hole in the front of the hood. Squeeze the bulb on the nebulizer, and let the bulb fully re-inflate before squeezing again. Count and take a note of how many times you squeeze the bulb before the test subject indicated they have recognized the taste inside their hood. When you administer the fit test with the respirator, use the same number of repetitions or slightly more before deciding whether the seal is sufficient. As a rule, if it takes between 1 and 10 squeezes, 10 squeezes should be used for the next test. If it takes more than 30 squeezes, the alternative (either bitter or sweet) test should be administered to the worker.

Time should be taken to let the taste clear from the worker's mouth before beginning to administer the fit test. A drink of water may speed this process along.

To administer the fit test allow the test subject to put on their respirator plus and glasses or other personal protective equipment that may affect the fit of the mask. Explain the test and tell them you'll be asking them to move their head around, up and down, side to side inside the hood to simulate normal work movement. They will be bending at the waist as well, this is necessary to test the seal of the mask in as wide a range of movements as possible.

Next use the nebulizer to administer about half of the total number of squeezes this particular subject required to recognize the solution in the sensitivity test. Mark the time on your watch when you start. Administer another half of the repetitions after each 30-second period for the duration of the test. The reason for this is the solution has a tendency to settle out of the hood in that amount of time.

After one minute while continuing to add solution to the hood, ask the subject to begin deep, full breathing. Tell them to be careful not to hyperventilate. If your subjects start passing out, you'll never get through all these employees. That's a joke. Just checking to see you are still paying attention.

After one minute of deep breathing, ask the test subject to start turning their head side to side. Have them pause at the end of each turn for a deep breath. After one minute of this procedure, have them do the same thing, but move their head up and down. Have them inhale each time their head is in the up position. After one minute of this, next you'll have the subject bend at the waist like they are touching their toes.

Again, top up the concentration and give them the user instructions to read out loud. Have them reread the passage for a full minute. You will likely be able to recite this passage by heart after only a few test subjects. Finally, ask the test subject to carry out one more minute of normal breathing.

Once the worker has completed all of these tasks without tasting the mist, they have passed the test. If at any time the worker does taste the solution, take the hood off the subject, take the respirator off, clear the pallet, re-administer the sensitivity test, then make adjustments to the respirator and re-administer the entire fit test.

Two failed tests is likely to indicate that the type of respirator being used is unsuitable for the particular facial structure of the test subject. Another size or model of respirator should be tried using the same testing techniques. A record of the testing process for each employee should be kept as part of the administration of the respirator fit testing process.

After testing the nebulizers should be rinsed out with clean water and wiped dry. Replacement 3M FT-13 Fit Test Nebulizers, 3M Fit Test Collars, and Sensitivity Solution are available.

If you have any questions about administering your fit test, or with the fit testing equipment, please don't hesitate to call us or contact us online Monday through Friday 7am till 5pm PST.

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