Best for half masks
Qualitative (QLFT)
Allowed for negative-pressure air-purifying respirators that need a fit factor of 100 or less — the N95s and elastomeric half masks most crews wear.
Notice
Qualitative vs quantitative fit testing
Published 2026-10-18 · 8 min read · sources checked 2026-10-18
Construction has no respirator standard of its own. 1926.103 says the construction requirements are identical to 1910.134, and that rule allows exactly two kinds of fit test. Which one you need depends on the facepiece, not on preference.
Required for full facepieces
Quantitative (QNFT)
A tight-fitting full facepiece passes only at a measured fit factor of 500 or more, and only an instrument can measure that.
Best evidence
Quantitative (QNFT)
A number on a record beats a yes/no that depends on whether the wearer tasted something.
The comparison, line by line
| Line | Qualitative | Quantitative |
|---|---|---|
| How fit is judged | The wearer reports a taste, smell or cough through a leak | An instrument measures a fit factor |
| Pass criterion | No detection of the test agent through the exercises | ≥ 100 half facepiece · ≥ 500 full facepiece |
| Respirators it may clear | Negative-pressure APRs needing a fit factor of 100 or less | Any tight-fitting facepiece |
| Accepted protocols | Isoamyl acetate · saccharin · Bitrex · irritant smoke | Generated aerosol · ambient aerosol CNC (incl. two modified versions) · CNP · CNP REDON |
| Exercises | Eight standard exercises, one minute each (grimace 15 s) | Same eight, except the modified CNC and CNP protocols, which set their own |
| What goes on the record | Pass/fail | Fit factor plus a strip chart or other recording |
| How often | Before first use, on any facepiece change, at least annually | Same |
Read from 29 CFR 1910.134(f), (m)(2) and Appendix A on 2026-10-18.
Before either test: the medical evaluation
The order is fixed. 1910.134(e)(1) requires a medical evaluation of the employee’s ability to use a respirator before the employee is fit tested or required to wear one. A fit tester who seals a mask on someone nobody has cleared has run the steps backwards. Track both dates side by side on the training matrix.
And the face has to be able to seal. Tight-fitting facepieces may not be worn by employees with facial hair between the sealing surface and the face, or with any condition that interferes with the seal. Stubble that grew in over a long weekend is the most common way a passed fit test stops meaning anything.
Qualitative fit testing
A hood, a nebuliser and the wearer’s own senses. Appendix A accepts four agents: isoamyl acetate (smell), saccharin and Bitrex (taste), and irritant smoke, which uses the body’s involuntary reaction to the irritant. Isoamyl acetate is not appropriate for particulate respirators unless the respirator is fitted with an organic vapour filter, which is why the taste tests dominate on construction sites.
The limit is written into the rule: QLFT may only be used to fit test negative-pressure air-purifying respirators that must achieve a fit factor of 100 or less (1910.134(f)(6)). Half masks — filtering facepieces and elastomeric half masks — sit inside that limit; their assigned protection factor in Table 1 is 10. That covers most silica Table 1 tasks that call for a respirator.
Caution
A taste test only works on someone who can taste the agent. Every protocol starts with a sensitivity screening without the respirator; a wearer who cannot detect the agent at screening needs a different agent or a quantitative test.
Quantitative fit testing
An instrument compares the concentration outside the mask with the concentration inside — a fit factor, defined in 1910.134(b) as “a quantitative estimate of the fit of a particular respirator to a specific individual.” The pass marks are 100 for a half facepiece and 500 for a full facepiece ((f)(7)).
That 500 is why the choice is not free. A full-facepiece air-purifying respirator carries an assigned protection factor of 50 in Table 1, five times a half mask’s 10. Clearing it for that job needs a measured fit factor that a pass/fail taste test, capped at 100, cannot show. Powered and supplied-air tight-fitting facepieces are tested in negative-pressure mode either way ((f)(8)).
The accepted QNFT protocols are a generated aerosol in a chamber, ambient aerosol counted by a condensation nuclei counter (CNC) — plus two modified CNC protocols with shorter exercise sets — and controlled negative pressure (CNP), including CNP REDON.
When to test again
- Before initial use, with the same make, model, style and size that will be worn.
- Whenever a different facepiece is used — size, style, model or make. A new supplier’s N95 is a new test.
- At least annually.
- On changes that could affect fit: facial scarring, dental changes, cosmetic surgery, an obvious change in body weight ((f)(3)).
Respirators are a PPE requirement with a written program behind them, and the hazard assessment is where the choice of facepiece should be recorded. If the hazard is a chemical, section 8 of its safety data sheet names the protection the manufacturer recommends.
The rule text
Quoted from the current eCFR text of title 29, read on 2026-10-18.
The employer shall ensure that an employee using a tight-fitting facepiece respirator is fit tested prior to initial use of the respirator, whenever a different respirator facepiece (size, style, model or make) is used, and at least annually thereafter.
QLFT may only be used to fit test negative pressure air-purifying respirators that must achieve a fit factor of 100 or less.
If the fit factor, as determined through an OSHA-accepted QNFT protocol, is equal to or greater than 100 for tight-fitting half facepieces, or equal to or greater than 500 for tight-fitting full facepieces, the QNFT has been passed with that respirator.
The employer shall establish a record of the qualitative and quantitative fit tests administered to an employee including: (A) The name or identification of the employee tested; (B) Type of fit test performed; (C) Specific make, model, style, and size of respirator tested; (D) Date of test; and (E) The pass/fail results for QLFTs or the fit factor and strip chart recording or other recording of the test results for QNFTs.