Respirator fit testing procedures

The employer must provide a sufficient number of respirator models and sizes so the test subject can pick the most acceptable respirator that fits correctly. This is required by the fit test selection rule in 1910.134AppA Part I.A.1. Employers should stock multiple sizes and shapes of each model to reasonably ensure an employee can find an acceptable fit. See also the general Respiratory Protection Standard at 1910.134.

You must show the employee how to put the respirator on, position it on the face, set strap tension, and decide whether the fit is acceptable before respirator selection. The appendix requires this pre-selection demonstration and availability of a mirror during selection in 1910.134AppA Part I.A.2. This demonstration is a brief review and does not replace formal respirator training required by 1910.134.

The test subject should hold facepieces up to the face, eliminate those that clearly do not fit, note the more acceptable facepieces, pick the most comfortable one, and wear it at least five minutes to assess comfort. Those steps are described in 1910.134AppA A.4–A.5. If unfamiliar with a model, the subject should don it several times and adjust straps to learn proper tension. See also the respirator selection requirement in 1910.134.

Comfort and fit should be assessed by reviewing nose position, room for eye protection, room to talk, position on face and cheeks, strap tension, tendency to slip, and self-observation in a mirror. These assessment criteria are listed in 1910.134AppA A.6–A.7. Use these points during the five-minute wear-and-assess period to decide if the respirator is acceptable. The employer must also ensure the respirator, when fitted and used properly, provides adequate protection per 1910.134.

The test subject must perform a user seal check either using the negative and positive pressure checks described in Appendix B-1 or a manufacturer-recommended procedure that provides equivalent protection. Appendix A requires this in 1910.134AppA A.8. The mask should be seated first by moving the head slowly while taking a few slow deep breaths; if the user check fails, the subject must select another facepiece and retest. See also 1910.134.

Fit testing must not be conducted if there is any hair growth or apparel that comes between the skin and the respirator sealing surface, such as beards, mustaches, sideburns, or stubble that crosses the seal. This prohibition is stated in 1910.134AppA A.9. Employers should require removal or alteration of items that interfere with a satisfactory seal. See also the sealing-surface requirements in 1910.134.

If an employee has difficulty breathing during the fit test, the employer must refer them to a physician or other licensed health care professional to determine if they can wear a respirator for their duties. Appendix A requires this referral in 1910.134AppA A.10. The employer should suspend the fit test for that employee until medical clearance or guidance is obtained in accordance with the medical evaluation provisions of 1910.134.

If the employee finds the fit unacceptable, they must be allowed to choose a different respirator and be retested. Appendix A states this right in 1910.134AppA A.11. Employers should keep a selection of alternate models/sizes on hand for immediate retesting. See also the general fit testing requirements at 1910.134.

The respirator must be worn for at least five minutes before the fit test begins, and the fit test must be performed while the subject is wearing any safety equipment that they would use during actual respirator use if that equipment could interfere with fit. These requirements are stated in 1910.134AppA A.12–A.13. Examples include goggles, face shields, or hard hats that would be worn during normal tasks. See 1910.134 for broader program requirements.

For most fit testing methods the required exercises are: normal breathing, deep breathing, turning head side to side, moving head up and down (inhale at up position), talking aloud, grimace (QNFT only), bending over (or jogging in place if bending is not possible), and normal breathing again; each exercise lasts one minute except the 15‑second grimace. These exercises and durations are specified in 1910.134AppA Part I.C.4(b) and the surrounding test-exercise guidance in 1910.134AppA. Note that the grimace is only required for quantitative fit testing (QNFT). See also 1910.134.

The grimace exercise (smile or frown for 15 seconds) is required only for quantitative fit testing (QNFT) and is not performed during qualitative fit testing (QLFT). This distinction is made in the test-exercise section of 1910.134AppA Part I.C. Employers must follow the correct exercise set depending on whether they use QLFT or QNFT as described in 1910.134.

If the fit testing environment (for example a shroud-type QNFT or QLFT unit) does not permit bending at the waist, jogging in place is an acceptable substitute for the bending exercise. Appendix A specifies this substitution in 1910.134AppA Part I.C. Ensure the substitute exercise still stresses the respirator fit similarly to the original exercise. See 1910.134 for overall fit-test method acceptability.

No — the respirator must not be adjusted once fit test exercises begin; any adjustment voids the test and it must be repeated. Appendix A requires this rule in the section that covers completion of the protocol and questioning the subject on comfort, found at 1910.134AppA. Employers should ensure proper donning, strap tension, and seating before starting the exercises. See 1910.134 for program requirements.

A person administering QLFT must be able to prepare test solutions, calibrate equipment, perform tests properly, recognize invalid tests, and keep test equipment in proper working order. Appendix A states these qualifications in the QLFT general requirements at 1910.134AppA B.1. Employers must ensure trained testers are used so that qualitative fit tests are valid and reliable, consistent with the employer responsibilities in 1910.134.

Before performing an isoamyl acetate (IAA) fit test, the subject must pass an odor-threshold screening (without wearing a respirator) to confirm they can detect IAA at low levels; if they cannot, the IAA QLFT must not be used. The odor-screening steps and requirements are described in the IAA protocol in 1910.134AppA Isoamyl Acetate Protocol. Employers must prepare the specified solutions and perform the screening in a separate, well-ventilated room to avoid olfactory fatigue. See also 1910.134.

If the IAA protocol is used to fit test a particulate respirator, that respirator must be equipped with an organic vapor cartridge because IAA is a vapor; Appendix A states this requirement in the IAA fit test notes in 1910.134AppA. In other words, particulate-only filters without an organic vapor cartridge are not appropriate for IAA testing. See 1910.134 for broader respirator selection rules.

The IAA fit test chamber should be a clear 55-gallon drum liner suspended inverted over a roughly 2-foot diameter frame with the top about 6 inches above the subject's head; if unavailable, similar construction using plastic sheeting is acceptable. These chamber specifications are described in the IAA fit test procedures in 1910.134AppA Isoamyl Acetate Fit Test. The inside top center should have a small hook for hanging the odor source. See 1910.134 for fit-test method acceptability.

The IAA solutions must be prepared in an area separate from the room where the subject will be tested to prevent olfactory fatigue; the screening room and the fit-test room should be well ventilated and separated. This preparation and room separation requirement is specified in the IAA odor-threshold and fit-test procedures in 1910.134AppA. Employers should also prepare fresh stock solution at least weekly per the protocol. See 1910.134.

Yes — the appendix carves out exceptions for the two modified ambient aerosol CNC quantitative fit testing protocols, the CNP protocol, and the CNP REDON protocol; those protocols require the specific exercise procedures listed in 1910.134AppA Part I.C.4(b), I.C.5(b), I.C.6(b), and I.C.7(b). For these specific quantitative protocols, employers must ensure test subjects perform the exercise procedures specified for that protocol rather than the general exercise set. See 1910.134AppA and the overall 1910.134 fit-testing requirements.

During the talking exercise the subject must talk out loud slowly and loud enough to be heard clearly by the test conductor, for example by reading the Rainbow Passage, counting backward from 100, or reciting a memorized poem or song. This talking requirement is described in the test-exercise list in 1910.134AppA Part I.C. The employer or test conductor should provide the text or instructions before starting the test. See 1910.134 for fit-test program obligations.

The test conductor must ask the subject about the comfort of the respirator after completing the protocol; if the respirator has become unacceptable, the subject must be allowed to try another model and be retested. Appendix A requires this post-test questioning in 1910.134AppA. Remember that any adjustment after the exercises voids the test and requires repeating it. See 1910.134.

No — if a test subject cannot correctly identify the jar containing the odor test solution during the odor-threshold screening, the IAA qualitative fit test must not be used for that person. The odor-threshold screening requirement is in the IAA protocol at 1910.134AppA. Employers must select an alternate OSHA-accepted fit test method (QLFT or QNFT) appropriate for that employee. See 1910.134 for acceptable fit-test methods.

If the respirator chosen as most comfortable proves unacceptable during user seal checks or fit testing, the subject must select another respirator and be retested. Appendix A requires this process in 1910.134AppA A.5–A.11. Employers should document which models provided acceptable fits and maintain a supply of alternate models and sizes. See also 1910.134.

The IAA fit test must be done in a room that is separate from the odor threshold screening and respirator selection room and that is well‑ventilated. The Appendix A to 1910.134 explicitly requires a separate, well‑ventilated test chamber to prevent contamination of other areas, and the same requirement is part of the respirator fit testing procedures in 1910.134.

• Use an exhaust fan or lab hood or similar ventilation to avoid general room contamination.
• Keep the IAA test area isolated from screening and selection areas to prevent cross‑contamination.

Yes — a copy of the test exercises and any prepared text must be taped to the inside of the test chamber. The Appendix A to 1910.134 requires that these materials be accessible inside the chamber so the subject can follow the exercise sequence, as also reflected in the respirator fit test procedures in 1910.134.

• This ensures consistent testing and lets the subject read or repeat the text during the exercises.

Provide the subject a single‑ply porous towel wetted with 0.75 ml of pure IAA hung on the chamber hook; an IAA swab or ampule may be substituted only if it has been demonstrated to produce an equivalent IAA concentration. The Appendix A to 1910.134 specifies a 6" by 5" paper towel folded and wetted with 0.75 ml IAA, and allows an ampule or swab as an alternative only when equivalence has been demonstrated, consistent with the fit testing requirements in 1910.134.

• Always follow an approved equivalence demonstration before using alternate IAA sources.
• Keep the towel material single‑ply and absorbent to standardize release rate.

Wait two minutes to allow the IAA concentration to stabilize before starting the fit test exercises. The Appendix A to 1910.134 directs a two‑minute stabilization period, and the respirator fit testing procedure in 1910.134 supports allowing time for the test atmosphere to equilibrate.

• Use this time to explain the test, demonstrate exercises, and emphasize the subject’s cooperation.

The test is failed immediately if the subject detects the banana‑like odor of IAA at any time during the fit test. The Appendix A to 1910.134 states detection of the IAA odor by the subject is a fail, and this requirement is part of the qualitative fit testing procedures in 1910.134.

• If the subject detects the odor, the subject must quickly exit the chamber to avoid olfactory fatigue (see next question).

The subject shall quickly exit the test chamber and leave the test area to avoid olfactory fatigue. The Appendix A to 1910.134 instructs subjects to exit promptly if they detect the IAA odor, and this procedure aligns with the respirator fit testing requirements in 1910.134.

• Prompt exit protects the subject’s sense of smell so later screening or fit tests remain valid.

If the subject fails, they must return to the selection room, remove the respirator, repeat the odor sensitivity (threshold) test, choose a different respirator, don it, and then repeat the full fit test procedure until a respirator that fits well is found. The Appendix A to 1910.134 describes this repeat‑and‑select process, which is part of the overall fit testing framework in 1910.134.

• If the odor sensitivity test is failed, the subject should wait at least 5 minutes before retesting to allow sensitivity to return.
• Continue this cycle until a passing respirator is found.

After passing the IAA fit test, the subject must demonstrate the respirator seal is effective by breaking the face seal and taking a breath before exiting the chamber. The Appendix A to 1910.134 requires this demonstration to confirm the test actually measured seal integrity, consistent with the respirator fit testing requirements in 1910.134.

• This intentionally exposes the subject to the test agent briefly to verify the test sensitivity and validity.

When the test subject leaves the chamber, they must remove the saturated towel and give it back to the test operator, and used towels must be kept in a self‑sealing plastic bag to prevent chamber contamination. The Appendix A to 1910.134 requires removing and bagging used towels to avoid buildup of IAA for subsequent tests, and this procedure supports the fit testing program requirements in 1910.134.

• Label and seal the bagged towels to control odor and contamination between test sessions.

The test enclosure must be about 12 inches in diameter by 14 inches tall with the front portion clear and a 3/4‑inch hole in front of the nose and mouth area for the nebulizer nozzle. The Appendix A to 1910.134 specifies these dimensions and features, and the fit testing procedures in 1910.134 reference a similar enclosure (for example, the 3M hood assembly, parts #FT 14 and #FT 15 combined).

• The enclosure should allow free head movement and have a clear front to observe breathing and reactions.

During threshold screening the subject shall breathe through their slightly open mouth with tongue extended and report immediately when they detect the sweet (saccharin) or bitter (Bitrex) taste. The Appendix A to 1910.134 prescribes this breathing method and reporting requirement, which supports accurate determination of taste sensitivity as required by 1910.134.

• The test conductor should instruct the subject in this posture before nebulizing the threshold solution.

The saccharin threshold check solution is prepared by dissolving 0.83 gram of sodium saccharin USP in 100 ml of warm water and is sprayed into the enclosure with a DeVilbiss Model 40 nebulizer by repeated squeezes. The Appendix A to 1910.134 provides this recipe and the nebulizer use protocol, which is part of the saccharin screening and fit testing procedures referenced in 1910.134.

• Start with 10 rapid squeezes; if no taste is reported, repeat up to two additional sets of 10 (for thresholds of 20 or 30 squeezes).
• Note the number of squeezes required to elicit a taste response; if no taste after 30 squeezes, the subject cannot use the saccharin method.

The saccharin fit test solution is prepared by adding 83 grams of sodium saccharin to 100 ml of warm water, and after the initial aerosol generation the concentration is replenished every 30 seconds using one‑half the original number of squeezes used initially. The Appendix A to 1910.134 gives the recipe and the replenishment schedule, which implements the qualitative fit test procedures in 1910.134.

• Use the number of initial squeezes determined in the threshold screening (10, 20, or 30) with a minimum of 10 squeezes.
• Then use half that number every 30 seconds during the exercises (e.g., 5, 10, or 15 squeezes).

Subjects may not eat, drink (except plain water), smoke, or chew gum for 15 minutes before the fit test. The Appendix A to 1910.134 requires this restriction for saccharin and Bitrex protocols to avoid interference with taste sensitivity, consistent with the fit testing framework in 1910.134.

• Ensure subjects are aware of this requirement when scheduling fit tests.

If nebulizer clogging is found at the end of the test session, the test is invalid; the operator must make periodic checks during testing to prevent clogging. The Appendix A to 1910.134 states that nebulizers tend to clog and that clogs detected after testing invalidate results, and this aligns with the fit testing responsibilities under 1910.134.

• Inspect nebulizers periodically during use and replace or clean if clogging is detected so tests remain valid.

The nebulizer shall be thoroughly rinsed in water, shaken dry, and refilled at least each morning and afternoon or at least every four hours. The Appendix A to 1910.134 prescribes this maintenance schedule for nebulizers used in saccharin and Bitrex testing, and this supports reliable fit testing under 1910.134.

• Regular maintenance reduces clogging and helps ensure consistent aerosol generation.

The Bitrex Threshold Check Solution is prepared by adding 13.5 milligrams of Bitrex to 100 ml of 5% salt (NaCl) solution in distilled water, and the Bitrex protocol otherwise follows the saccharin procedure. The Appendix A to 1910.134 gives this Bitrex recipe and instructs that the Bitrex fit test uses the saccharin protocol steps, which are part of the fit testing procedures in 1910.134.

• Use the same enclosure size, breathing posture, and squeeze sequencing as in the saccharin protocol.
• Note that Bitrex detects bitter taste while saccharin detects sweet taste.

A subject may proceed to the fit test only if they elicit a taste response during threshold screening within 30 squeezes; if no taste is reported after 30 squeezes, they may not use that taste method. The Appendix A to 1910.134 specifies the 30‑squeeze limit and the requirement to record the number of squeezes for fit test setup, consistent with the requirements in 1910.134.

• If threshold screening yields a response, record the squeeze count (10, 20, or 30) and use it to set the initial fit test aerosol concentration.

The minimum number of initial squeezes is 10, and the initial number is chosen based on the number of squeezes that produced a taste during the threshold screening (10, 20, or 30). The Appendix A to 1910.134 requires using the threshold result to set the initial fit test aerosol concentration with at least 10 squeezes, consistent with the qualitative fit test procedures in 1910.134.

• After the initial generation, replenish every 30 seconds with one half the original number of squeezes.

The test is passed if the subject does not report tasting the saccharin/Bitrex during the exercises; the test is failed if the subject reports tasting the agent at any time. The Appendix A to 1910.134 sets this pass/fail criterion, and these outcomes are part of the fit testing requirements in 1910.134.

• A failed test requires trying a different respirator and repeating the full screening and fit test procedure.

Prepare the Bitrex fit test solution exactly as specified and mark the nebulizer so it is not confused with the screening nebulizer. Under the Bitrex protocol in 1910.134AppA, the solution is made by adding 337.5 mg of Bitrex to 200 ml of a 5% salt (NaCl) solution in warm water, and the fit-test nebulizer must be clearly marked to distinguish it from the screening test nebulizer.

• Use the exact amounts (337.5 mg Bitrex + 200 ml of 5% NaCl warm water) to get the correct test concentration.
• Marking the nebulizer prevents mixing screening and fit-test equipment, as required by the protocol. See 1910.134AppA for the Bitrex recipe and marking requirement.

Use the same number of squeezes required during the screening test for the initial fit test aerosol, and replenish the aerosol every 30 seconds using half that number of squeezes. The Bitrex protocol in 1910.134AppA requires inserting the nebulizer into the enclosure and spraying an initial concentration using the number of squeezes that elicited a taste during screening (commonly 10, 20, or 30). After generating the aerosol and starting the exercises, the operator must replenish the aerosol every 30 seconds using one half the initial squeezes (for example, 5, 10, or 15).

• Match the initial squeezes to the individual’s screening response.
• Replenish on a 30-second cadence to maintain test challenge.

If the test subject tastes Bitrex during the fit test, the respirator fit test is failed and you must try a different respirator and repeat the full procedure. The Bitrex protocol in 1910.134AppA states that detection of the bitter taste at any time means the fit is unsatisfactory; the test is failed, and a different respirator must be tried with the entire test procedure (both taste-threshold screening and fit testing) repeated.

• Stop the test immediately if the subject reports tasting Bitrex.
• Don’t just adjust the respirator and continue — select a different make/model/size and perform a new screening plus fit test per the protocol.

Only stannic chloride smoke tubes may be used, the respirator must have HEPA or P100 filters, no hood/enclosure is used, and the test must be done with precautions to minimize smoke exposure. The irritant smoke protocol in 1910.134AppA requires that the respirator tested be equipped with HEPA or P100 filters, only stannic chloride smoke tubes be used, no form of hood or test enclosure be used, and the test conductor take steps to minimize subject exposure because the smoke can irritate eyes, lungs, and nasal passages.

• Ensure adequate ventilation so smoke does not build up or expose the conductor.
• Warn the subject about possible irritation and instruct them to keep their eyes closed during the test.

Perform a sensitivity screening so the subject demonstrates they can detect a weak concentration of the irritant smoke, with the subject allowed to smell a weak concentration before donning the respirator and instructed to keep eyes closed. The screening steps in 1910.134AppA require breaking both ends of the stannic chloride smoke tube, attaching one end to a low-flow pump set to deliver 200 milliliters per minute (or using an aspirator squeeze bulb), covering the jagged other end, advising the subject of irritation risks, and letting the subject smell a weak concentration of the smoke to confirm detection ability.

• Use the low-flow pump at ~200 ml/min (or squeeze bulb) to produce a weak, non-harmful concentration for screening.
• Instruct the subject to keep eyes closed and confirm they can detect the irritant properties before the respirator is donned.

Direct the smoke starting about 12 inches from the facepiece, move around the entire perimeter gradually to within 6 inches, perform the required exercises with the smoke continuously directed at six inches, and fail the test if the subject detects the smoke. The irritant smoke fit-test steps in 1910.134AppA instruct the operator to begin at least 12 inches from the facepiece and make multiple passes around the perimeter, moving to within 6 inches, then have the subject perform the exercises while the operator continually challenges the seal at six inches; if the subject reports the smoke (or has an involuntary response), the fit test is failed.

• Keep the subject’s eyes closed during the test.
• If the subject reports detection during the test, stop and fail that respirator; a full re-test (including sensitivity screening) is required with any retest per the protocol.

Set up QNFT equipment and test chamber so sampling is reliable, the in-mask probe draws from the breathing zone (midway between nose and mouth and at least 1/4 inch into the facepiece), tubing lengths/diameters are equal, concentration is stable to within 10%, and peak penetration limits are 5% for half masks and 1% for full facepieces. The QNFT requirements in 1910.134AppA state that the in-mask probe must sample midway between nose and mouth with the probe extending at least 1/4 inch into the facepiece cavity; sampling and chamber tubing must be equal in length and diameter; chamber concentration must be held to within a 10% variation; and immediately after entry the peak penetration must not exceed 5% for a half mask or 1% for a full facepiece, with the test terminated if any single peak exceeds those values.

• Ensure equipment is maintained, calibrated, and the operator can recognize invalid tests per 1910.134AppA.
• Have the wearer adjust straps without assistance to a comfortable fit and do not adjust the respirator once test exercises begin.