Qualitative Fit Testing
Our Quick Tips #140: Respirator Fit Testing Requirements and Procedures offers an overview of the Occupational Safety and Health Administration’s (OSHA’s) requirements for respirator fit testing. This document takes a closer look at the specific requirements for qualitative fit testing that OSHA details in Appendix A of their Respiratory Protection Standard, 29 Code of Federal Regulation (CFR) 1910.134.
All respirators that rely on a mask-to-face seal need to be tested on the wearer prior to first issue; when there’s a change in the model, style or size of respirator used; when there’s a physical facial change in the person wearing the mask; and at least annually thereafter. Qualitative fit testing is one of two broad categories of testing that OSHA recognizes. The other option is quantitative fit testing. The qualitative fit test procedures rely on a subjective sensation (taste, irritation, smell) of the respirator wearer to a particular test agent while the quantitative procedures measure actual face seal leakage. For more details on quantitative fit testing see Quick Tips #318: Quantitative Fit Testing.
OSHA allows the use of four different qualitative fit test protocols. The options 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®--a bitter tasting challenge agent).
Even though qualitative fit testing can be used to fit test both half-mask and full-face respirators, it is important to note that qualitative fit tests only validate an assigned protection (APF) of 10. OSHA has established an APF of 50 for full facepiece respirators but in order to use a full facepiece beyond 10 times the permissible exposure limit (PEL), a quantitative fit test must be performed.
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).
The test subject then performs either a positive pressure or negative pressure seal check on the facepiece. OSHA describes each seal check as:
- Positive pressure check. Close off the exhalation valve and exhale gently into the facepiece. The fit is considered satisfactory if a slight positive pressure can be built up inside the facepiece without any evidence of outward leakage of air at the seal. For most respirators this method of leak testing requires the wearer to first remove the exhalation valve cover before closing off the exhalation valve and then carefully replacing it after the test.
- Negative pressure check. Close off the inlet opening of the canister or cartridge(s) by covering with the palm of the hand(s) or by replacing the filter seal(s), inhale gently so that the facepiece collapses slightly, and hold the breath for 10 seconds. Since the design of the inlet opening of some cartridges cannot be effectively covered with the palm of the hand, the test can be performed by covering the inlet opening of the cartridge with a thin latex or nitrile glove. If the facepiece remains in its slightly collapsed condition and no inward leakage of air is detected, the tightness of the respirator is considered satisfactory.
Respirator manufacturer seal checks can be used in place of the OSHA described checks if the employer can prove they’re equally as effective.
Before beginning the qualitative fit testing protocol, employees are given a description of the fit test and their responsibilities during the procedure. Exercises that the test subject performs include:
- Normal breathing: standing position without talking.
- Deep breathing: standing position without talking and breathing slowly and deeply.
- Turning head side-to-side: standing position, slowly turning head side-to side, holding at extreme point and inhaling.
- Moving head up and down: standing position, slowly moving head up and down and inhaling in the up position.
- 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.
- 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.
- Normal breathing: standing position without talking.
Each test exercise is performed for one minute.
"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."
- Obtain three, one-liter glass jars with metal lids.
- Use odor-free water at approximately 25°C (77°F) for the solutions.
- Prepare the solutions in an area separate from the testing area to prevent olfactory fatigue in the test subject.
- In the first glass jar, prepare the isoamyl acetate stock solution by adding one-milliliter (mL) of pure isoamyl acetate to 800-mL of odor-free water. Put the lid on and shake for 30 seconds. New solution must be prepared at least weekly.
- 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.
- In the third jar, prepare a test blank by placing 500-mL of odor-free water into the jar.
- 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.
- Conduct the screening test in a room separate from the room used for actual testing. The two rooms should be well ventilated and may not be connected to the same recirculating ventilation system.
- Type the following instructions and place on a table in front of the two test jars: "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 and 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."
- 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.
- If the test subject correctly identifies the jar containing the odor test solution, he/she may proceed to respirator selection and fit testing.
- Take a 24-inch round piece of circular cardboard and cut a two-inch slit in the center.
- Slide the hook of a wire coat hanger through the slit.
- 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.
- The hook of the wire coat hanger should now support the inverted plastic bag and form a test chamber.
- 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.
- Tape a copy of the test exercises and any prepared text to the inside of the test chamber.
- Each respirator used for the fitting and fit testing must be equipped with organic vapor cartridges or offer protection against organic vapors.
- 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.
- Each test subject should wear his or her respirator for at least ten minutes before starting the test.
- Upon entering the test chamber, the test subject is given a six inch by five inch piece of paper towel (or other porous absorbent single ply material) folded in half and wetted with 0.75-mL of pure isoamyl acetate.
- The test subject hangs the wet towel with a clip or over the hanger inside the top of the test chamber.
- 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.
- Each exercise must be performed for at least one minute.
- 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.
- Upon returning to the selection room, the test subject removes the respirator, repeats the odor sensitivity test, selects and dons another respirator, returns to the test chamber, etc. This process continues until a respirator that fits correctly has been found. Should the subject fail the odor sensitivity test, he/she should wait about five minutes before retesting.
- When a respirator is found that passes the test, the subject must demonstrate the efficiency of the test procedure by breaking the face seal and taking a breath before exiting the chamber. This is done to verify that he/she can still detect the banana-like odor.
- When the test subject leaves the test chamber he/she removes the saturated towel and returns it to the test conductor. The test conductor places the towel in a self-sealing bag.
**To purchase a ready-made fit test enclosure see Grainger’s fit testing hoods.
- Performed without wearing a mask.
- Intended to determine whether the test subject can detect the taste of saccharin or Bitrex.
- During threshold screening as well as during qualitative fit testing, subjects must wear an enclosure over the head and shoulders that is approximately 12 inches in diameter by 14 inches tall. At least the front portion must be clear and allow 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.
- Test subject steps into the test enclosure.
- During the screening, test subjects must breathe through their slightly open mouth with their tongue slightly extended.
- Subjects are instructed to report when they detect a sweet or bitter taste.
- Using a DeVilbiss Model 40 Inhalation Medication Nebulizer or equivalent, the test conductor sprays a threshold check solution into the enclosure.
- The nebulizer must be clearly marked as taste threshold or sensitivity test nebulizer.
- The nozzle of nebulizer is directed away from the nose and mouth of the test subject.
- 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 five percent sodium chloride solution.
- To produce the aerosol, the nebulizer bulb is firmly squeezed so that it collapses completely, then released and allowed to fully expand.
- Ten squeezes are repeated rapidly, and then the test subject is asked whether the saccharin or Bitrex can be tasted.
- If the test subject reports tasting the sweet or bitter taste during the ten squeezes, the screening test is completed.
- The taste threshold is noted as ten regardless of the number of squeezes actually completed.
- 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.
- If the test subject reports tasting the sweet or bitter taste during the second ten squeezes, the screening test is completed.
- The taste threshold is noted as twenty regardless of the number of squeezes actually completed.
- 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.
- If the test subject reports tasting the sweet or bitter taste during the third set of ten squeezes, the screening test is completed.
- The taste threshold is noted as thirty regardless of the number of squeezes actually completed.
- 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.
- Test subjects may not eat, drink (except plain water), smoke or chew gum for 15 minutes before the test.
- The fit test uses the same enclosure as used for the taste threshold screening.
- Test subjects don the enclosure while wearing the selected respirator.
- The respirator must be properly adjusted and equipped with a particulate filter(s).
- A second DeVilbiss Model 40 Inhalation Medication Nebulizer or equivalent is used to spray the fit test solution into the enclosure.
- This nebulizer must be clearly marked to distinguish it from the screening test solution nebulizer.
- 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.
- 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.
- 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.
- After generating the aerosol, the test subjects are instructed to perform the test exercises.
- 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.
- If the test subject does not report tasting the saccharin or Bitrex, the test is passed.
- 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).
- 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.
Step One: 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.
- The respirator to be tested must be equipped with a P100 rated particulate series filter(s).
- Only stannic chloride smoke tubes are used for this type of fit testing.
- No form of test enclosure or hood for the test subject is used.
- The smoke can be irritating to the eyes, lungs and nasal passages. The test conductor must 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 must 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.
- The fit test must 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.
- The person to be tested must demonstrate his or her ability to detect a weak concentration of the irritant smoke.
- The test operator breaks 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-mL per minute or to an aspirator squeeze bulb.
- The test operator covers 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.
- The test operator advises 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.
- The test subject must 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 must carefully direct a small amount of the irritant smoke in the test subject's direction to determine that he/she can detect it.
- The person being fit tested dons the respirator without assistance and performs the required user seal check(s).
- The test subject must be instructed to keep his/her eyes closed if wearing a half-mask respirator.
- Using the low flow pump or the squeeze bulb, the test operator directs a stream of irritant smoke from the smoke tube toward the face seal area of the test subject.
- The test operator begins at least 12" from the facepiece and moves the smoke stream around the whole perimeter of the mask.
- The operator gradually makes two more passes around the perimeter of the mask, moving to within six inches of the respirator.
- If the person being tested has not had an involuntary response and/or detected the irritant smoke, proceed with the test exercises.
- The test subject performs the test exercises while the respirator seal is continually challenged by smoke which is directed around the perimeter of the respirator at a distance of six inches.
- 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.
- Each test subject who passes the irritant smoke test without evidence of a response (involuntary cough, irritation) must 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 voids the fit test.
- 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 Tip #140: Respirator Fit Testing Requirements and Procedures.
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