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Qualitative Fit Testing

Quick Tips #324

When qualitative fit testing negative pressure respirators, a variety of testing agents can be used and are acceptable to the Occupational Safety and Health Administration (OSHA). The most common types are isoamyl acetate (commonly referred to as banana oil because of its fruit-like aroma), saccharin (a sweet-tasting agent), irritant smoke (stannic chloride) and Denatonium Benzoate (also known as Bitrex). Bitrex leaves a very bitter taste in the mouth of fit test subjects whose masks do not fit properly.

The qualitative fit testing method is the most widely used method for respirator fit testing. This method is acceptable to OSHA standards (29 CFR 1910.134) and can be performed with minimal training and expense. Even though qualitative fit testing can be used to fit test both half-mask and full-face respirators, it is important to note that you are only verifying a 10X assigned protection factor (APF) on both half-mask and full-face respirators. To verify a higher APF on a full-face respirator, you must perform a quantitative fit test (QNFT). See Quick Tips #318: Quantitative Fit Testing.

Prior to selecting a respirator, employees are shown how to put on a respirator, how to position it on the face, how to adjust the strap tension, and how to determine an acceptable fit. The employee then picks the most acceptable respirator from a sufficient number of samples and wears it at least five minutes to assess the comfort (chin properly placed, adequate strap tension, fits across the nose bridge, spans the distance from the nose to chin and does not have a tendency to slip). Positive pressure and negative pressure seal checks are then performed.

Positive pressure seal check:

  • Close off the exhalation vale
  • Exhale gently into the facepiece
  • Satisfactory if slight positive pressure is noticed

Negative pressure seal check:

  • Close off the inlet openings
  • Inhale gently and hold breathe for 10 seconds
  • Satisfactory if facepiece collapses

Before beginning the qualitative fit testing protocol, employees are given a description of the fit test and their responsibilities during the procedure. Excercises that the test subject performs include:

  1. Normal breathing: standing position without talking
  2. Deep breathin: standing position without talking and breathing slowly and deeply
  3. Turning head side-to-side: standing position, slowly turning head side-to side, holding at extreme point and inhaling
  4. Moving head up and down: standing position, slowly moving head up and down and inhaling in the up position
  5. Talking: talk out loud slowly and loud enough to be heard clearly; read from a prepared text (Rainbow Passage*); count backward from 100 or recite a memorized poem
  6. Bending over / jogging in place: bend at the waist as if to touch toes.  Jogging in place is substituted for testing done in a shroud that does not permit bending over at the waist
  7. Normal breathing: standing position without talking

Each test excercise is performed for one minute.

*Rainbow Passage

"When the sunlight strikes raindrops in the air, they act like a prism and form a rainbow. The rainbow is a division of white light into many beautiful colors. These take the shape of a long, round arch with its path high about, and its two ends apparently beyond the horizon. There is, according to legend, a boiling pot of gold at one end. People look, but no one ever finds it. When a man looks for something beyond reach, his friends say he is looking for the pot of gold at the end of the rainbow."

Isoamyl Acetate/Banana Oil Protocol

  1. Prepare the solutions
    1. Obtain three one-liter glass jars with metal lids.
    2. Use odor-free water at approximately 25°C (77°F) for the solutions.
    3. Prepare the solutions in an area separate from the testing area to prevent olfactory fatigue in the test subject.
    4. In the first glass jar, prepare the isoamyl acetate stock solution by adding one-milliliter (mL) of pure isoamyl acetate to 800mL of odor-free water. Put the lid on and shake for 30 seconds. New solution must be prepared at least weekly.
    5. In the second jar, prepare the odor test solution by placing 0.4-mL of the stock solution into 500-mL of odor-free water. Shake for 30 seconds and allow to stand for two to three minutes so that the isoamyl acetate concentration may reach equilibrium. This solution may be used for one day only.
    6. In the third jar, prepare a test blank by placing 500-mL of odor-free water into the jar.
    7. Label the odor test solution and test blank jars 1 and 2. If the labels are put on the lids, they can be periodically switched to avoid test subjects recognition of the odor test jar.
  2. Perform the odor threshold screening
    1. Conduct the screening test in a room separate from the room used for actual testing. The two rooms should be well ventilated, but may not be connected to the same recirculating ventilation system.
    2. Type the following instruction and place on a table in front of the two test jars (jars labeled 1 and 2):
      "The purpose of this test is to determine whether you can smell banana oil at a low concentration. The two bottles in front of you contain water. One of these bottles also contains a small amount of banana oil. Be sure the covers are on tight, then shake each bottle for two seconds. Unscrew the lid of each bottle one at a time and sniff at the mouth of the bottle. Indicate to the test conductor which bottle contains banana oil."
    3. If the test subject is unable to correctly identify the jar containing the odor test solution, the isoamyl acetate qualitative fit test (QLFT) may not be used. d. If the test subject correctly identifies the jar containing the odor test solution, he may proceed to respirator selection and qualitative fit testing.
    4. If the test subject correctly identifies the jar containing the odor test solution, he may proceed to respirator selection and fit testing.
  3. Make a test chamber**
    1. Take a 24-inch round piece of circular cardboard and cut a 2-inch slit in the center.
    2. Slide the hook of a wire coat hanger through the slit.
    3. Invert a plastic bag (clear 55 gallon garbage bag) over the cardboard and puncture the center of what would normally be the bottom of the plastic bag with the hook portion of the wire coat hanger.
    4. The hook of the wire coat hanger should now support the inverted plastic bag and form a test chamber.
    5. Suspend the test chamber from the ceiling of the fit test area with the length of heavy string so that the chamber can be adjusted to the height of the employee being tested. The top of the test chamber should be about six inches above the test subject's head.
    6. Tape a copy of the test exercises and any prepared text to the inside of the test chamber.
  4. Respirator selection and use
    1. Each respirator used for the fitting and fit testing must be equipped with organic vapor cartridges or offer protection against organic vapors.
    2. After selecting, donning and properly adjusting a respirator by him/herself, the test subject wears the respirator to the fit test room. The fit test room must be separate from the room used for odor threshold screening and respirator selection and should be ventilated by an exhaust fan or lab hood to prevent general room contamination.
    3. Each test subject should wear his or her respirator for at least ten minutes before starting the test.
  5. Qualitative fit testing
    1. Upon entering the test chamber, the test subject is given a 6" x 5" piece of paper towel (or other porous absorbent single ply material) folded in half and wetted with 0.75-mL of pure isoamyl acetate.
    2. The test subject hangs the wet towel with a clip or over the hanger inside the top of the test chamber.
    3. Allow two minutes for the isoamyl acetate test concentration to stabilize before starting the fit test exercises. This would be an appropriate time to talk with the test subject to explain the fit test, the importance of his/her cooperation, the purpose for the exercises and to demonstrate some of the exercises.
    4. Each exercise must be performed for at least one minute.
    5. If at any time during the test, the test subject detects the banana-like odor of isoamyl acetate, the test is failed and the test subject must quickly exit the test chamber and leave the test area to avoid olfactory fatigue.
    6. Upon returning to the selection room, the test subject removes the respirator, repeats the odor sensitivity test, select and dons another respirator, returns to the test chamber, etc. This process continues until a respirator that fits correctly has been found. Should the odor sensitivity test be failed, the subject should wait about five minutes before retesting.
    7. When a respirator is found that passes the test, the efficiency of the test procedure must be demonstrated by having the subject break the face seal and take a breath before exiting the chamber.
    8. When the test subject leaves the test chamber he/she removes the saturated towel – and return it to the test conductor. The test conductor places the towel in a self-sealing bag.

**To purchase a ready-made fit test tent, order a respirator fit test tent. Grainger also carries a large selection of Fit Testing Hoods and Enclosures.

Saccharin Solution and Bitrex™ Solution Protocol

  1. Taste threshold screening
    1. Performed without wearing a mask.
    2. Intended to determine whether the test subject can detect the taste of saccharin or Bitrex™.
    3. During threshold screening as well as during qualitative fit testing, subjects must wear an enclosure about the head and shoulders that is approximately 12 inches in diameter by 14 inches tall with at least the front portion clear and that allows free movements of the head when a respirator is worn.  The test enclosure must have a 3/4-inch (1.9 cm) hole in front of the test subject's nose and mouth area to accommodate a nebulizer nozzle.
    4. Test subject steps into the test enclosure.
    5. During the screening test subjects must breathe through their slightly open mouth with their tongue slightly extended.
    6. Subjects are instructed to report when they detect a sweet or bitter taste.
    7. Using a DeVilbiss Model 40 Inhalation Medication Nebulizer or equivalent, the test conductor sprays a threshold check solution into the enclosure.
    8. The nebulizer must be clearly marked as taste threshold or sensitivity test nebulizer.
    9. The nozzle of nebulizer is directed away from the nose and mouth of the test subject.
    10. The threshold check solution is prepared by dissolving 0.83 gram (gr) of sodium saccharin USP in 100-ml of warm water or 13.5-milligrams (mg) of Bitrex™ in 100-mL of 5% sodium chloride solution. 
    11. To produce the aerosol, the nebulizer bulb is firmly squeezed so that it collapses completely, then released and allowed to fully expand.
    12. Ten squeezes are repeated rapidly and then the test subject is asked whether the saccharin or Bitrex™ can be tasted. 
    13. If the test subject reports tasting the sweet or bitter taste during the ten squeezes, the screening test is completed.
    14. The taste threshold is noted as ten regardless of the number of squeezes actually completed.
    15. If the first response is negative, ten more squeezes are repeated rapidly and the test subject is again asked whether the saccharin or Bitrex™ is tasted.
    16. If the test subject reports tasting the sweet or bitter taste during the second ten squeezes, the screening test is completed.
    17. The taste threshold is noted as twenty regardless of the number of squeezes actually completed.
    18. If the second response is negative, ten more squeezes are repeated rapidly and the test subject is again asked whether the saccharin or Bitrex™ is tasted.
    19. If the test subject reports tasting the sweet or bitter taste during the third set of ten squeezes, the screening test is completed.
    20. The taste threshold is noted as thirty regardless of the number of squeezes actually completed.
    21. If the saccharin or Bitrex™ is not tasted after 30 squeezes,  the test subject is unable to taste saccharin or Bitrex™ and may not perform the saccharin or Bitrex™ fit test.
  2. Qualitative fit testing
    1. Test subjects may not eat, drink (except plain water), smoke, or chew gum for 15 minutes before the test.
    2. The fit test uses the same enclosure as used for the taste threshold screening.
    3. Test subjects don the enclosure while wearing the selected respirator. 
    4. The respirator must be properly adjusted and equipped with a particulate filter(s).
    5. A second DeVilbiss Model 40 Inhalation Medication Nebulizer or equivalent is used to spray the fit test solution into the enclosure.
    6. This nebulizer must be clearly marked to distinguish it from the screening test solution nebulizer.
    7. The fit test solution is prepared by adding 83-gr of sodium saccharin to 100-ml of warm water or 337.5-mg of Bitrex™ to 200-ml of a 5% sodium chloride solution in warm water.
    8. As before, the test subjects must breathe through their slightly open mouth with tongue extended, and report if he/she tastes the sweet taste of saccharin or bitter taste of Bitrex™.
    9. The nebulizer is inserted into the hole in the front of the enclosure and an initial concentration of fit test solution is sprayed into the enclosure using the same number of squeezes (either 10, 20 or 30 squeezes) based on the number of squeezes required to elicit a taste response as noted during the screening test.   A minimum of 10 squeezes is required.
    10. After generating the aerosol, the test subjects are instructed to perform the test exercises.
    11. Every 30 seconds the aerosol concentration is replenished using one-half the original number of squeezes used initially (e.g., 5, 10 or 15). ?The test subjects must indicate to the test conductor if at any time during the fit test the taste of saccharin or Bitrex™ is detected.
    12. If the test subject does not report tasting the saccharin or Bitrex™, the test is passed.
    13. If the taste of saccharin or Bitrex™ is detected, the fit is deemed unsatisfactory and the test is failed. A different respirator must be tried and the entire test procedure is repeated (taste threshold screening and fit testing).
    14. Since the nebulizers have a tendency to clog during use, the test conductor must make periodic checks of the nebulizer to ensure that it is not clogged. If clogging is found at the end of the test session, the test is invalid.

Irritant Smoke / Stannic Chloride

  1. This qualitative fit testing uses a person's response to the irritating chemicals released in the "smoke" produced by a stannic chloride ventilation smoke tube to detect leakage into the respirator.
    1. The respirator to be tested shall be equipped with a P100 rated particulate series filter(s).
    2. Only stannic chloride smoke tubes shall be used for this type of fit testing.
    3. No form of test enclosure or hood for the test subject shall be used.
    4. The smoke can be irritating to the eyes, lungs and nasal passages. The test conductor shall take precautions to minimize the test subject's exposure to irritant smoke. Sensitivity varies, and certain individuals may respond to a greater degree to irritant smoke. Care shall be taken when performing the sensitivity screening checks that determine whether the test subject can detect irritant smoke to use only the minimum amount of smoke necessary to elicit a response from the test subject.
    5. The fit test shall be performed in an area with adequate ventilation to prevent exposure of the person conducting the fit test or the build-up of irritant smoke in the general atmosphere.
  2. Sensitivity screening check
    1. The person to be tested must demonstrate his or her ability to detect a weak concentration of the irritant smoke.
    2. The test operator shall break both ends of a stannic chloride smoke tube and attaches one end of the smoke tube to a low flow air pump set to deliver 200 milliliters per minute, or to an aspirator squeeze bulb.
    3. The test operator shall cover the other end of the smoke tube with a short piece of tubing to prevent potential injury from the jagged end of the smoke tube.
    4. The test operator shall advise the test subject that the smoke can be irritating to the eyes, lungs, and nasal passages and instructs the subject to keep his/her eyes closed while the test is performed.
    5. The test subject shall be allowed to smell a weak concentration of the irritant smoke before the respirator is donned to become familiar with its irritating properties and to determine if he/she can detect the irritating properties of the smoke. The test operator shall carefully direct a small amount of the irritant smoke in the test subject's direction to determine that he/she can detect it.
  3. Irritant smoke qualitative fit testing procedure
    1. The person being fit tested shall don the respirator without assistance, and perform the required user seal check(s).
    2. The test subject shall be instructed to keep his/her eyes closed if wearing a half-mask respirator.
    3. The test operator shall direct a stream of irritant smoke from the smoke tube toward the face seal area of the test subject, using the low flow pump or the squeeze bulb.
    4. The test operator shall begin at least 12" from the face piece and move the smoke stream around the whole perimeter of the mask.
    5. The operator shall gradually make two more passes around the perimeter of the mask, moving to within six inches of the respirator.
    6. If the person being tested has not had an involuntary response and/or detected the irritant smoke, proceed with the test exercises.
    7. The test exercises are performed by the test subject while the respirator seal is being continually challenged by the smoke, directed around the perimeter of the respirator at a distance of six inches.
    8. If the person being fit tested reports detecting the irritant smoke at any time, the test is failed and the person being tested must repeat the entire sensitivity check and fit test procedure.
    9. Each test subject passing the irritant smoke test without evidence of a response (involuntary cough, irritation) shall be given a second sensitivity screening check, with the smoke from the same smoke tube used during the fit test, once the respirator has been removed, to determine whether he/she still reacts to the smoke. Failure to evoke a response shall void the fit test.
    10. If a response is produced during this second sensitivity check, then the fit test is passed.

For more information on general fit testing procedures, please refer to Quick Tips #140: Respirator Fit Testing.


29 CFR 1910.134 Respiratory Protection Standard
Fit Test Kits

(Rev. 1/2012)

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