Free lesson · 2 min read · Updated 2026-10-25
Respirator Selection and Fit Testing for HAZWOPER Work
Respirators are covered by their own OSHA standard, 29 CFR 1910.134, which applies on top of HAZWOPER. Any employer that requires respirators needs a written respiratory protection program run by a qualified program administrator.
Before anyone wears a respirator
- Medical evaluation by a physician or other licensed health care professional, using the OSHA questionnaire or an equivalent exam, to confirm the worker can breathe through one.
- Fit test with the exact make, model, style and size of tight-fitting facepiece the worker will use.
- Training on why the respirator is needed, its limits, how to put it on, check it, maintain it and store it.
Two families of respirators
- Air-purifying respirators (APRs) filter or absorb contaminants from the surrounding air: filtering facepieces, half and full-face elastomeric masks with cartridges, and powered air-purifying respirators (PAPRs). They need at least 19.5% oxygen and can't be used in IDLH atmospheres.
- Atmosphere-supplying respirators provide clean air from a separate source: self-contained breathing apparatus (SCBA) or supplied-air (airline) respirators. These are used for oxygen-deficient, IDLH or unknown atmospheres.
Assigned protection factors
An assigned protection factor (APF) is the level of protection a properly working, properly fitted respirator is expected to give. OSHA's table in 1910.134(d)(3)(i)(A) includes:
| Respirator | APF |
|---|---|
| Filtering facepiece or elastomeric half mask (air-purifying) | 10 |
| Full facepiece air-purifying | 50 |
| PAPR with loose-fitting facepiece | 25 |
| PAPR with full facepiece | 1,000 |
| SCBA, pressure-demand, full facepiece | 10,000 |
Maximum use concentration
The maximum use concentration (MUC) is the highest airborne concentration a respirator can be used in. Multiply the APF by the exposure limit. A half mask (APF 10) against a vapor with an exposure limit of 50 ppm has an MUC of 500 ppm. If air monitoring shows higher readings, step up to a respirator with a higher APF. Never use an APR above the IDLH concentration, whatever the math says.
Filters and cartridges
- Particulate filters are rated N (not oil resistant), R (somewhat oil resistant) or P (strongly oil resistant), with efficiency 95, 99 or 100 (99.97%). P100 filters are magenta.
- Chemical cartridges are matched to the contaminant: organic vapor cartridges are black, acid gas white, ammonia/methylamine green, and combination cartridges carry more than one color.
- Gas and vapor cartridges need an end-of-service-life indicator or a written change schedule based on objective data. Odor is not an acceptable warning.
Fit testing and seal checks
- Fit testing happens before first use, at least every 12 months, and whenever the worker's face changes in a way that could affect fit (for example, major weight change or dental work).
- Qualitative fit tests use a test agent the wearer can taste or smell (saccharin, Bitrex) or that causes irritation. Quantitative fit tests use an instrument to measure leakage numerically.
- Do a user seal check (positive and negative pressure) every time you put on a tight-fitting respirator.
- Facial hair that comes between the sealing surface and the face isn't allowed with tight-fitting respirators.
Respirators and HAZWOPER PPE levels
Level A and B ensembles use SCBA or supplied air. Level C uses an APR, which is only allowed when contaminants and concentrations are known. Try the respirator quiz.
Frequently asked questions
How often is respirator fit testing required?
Before first use, at least every 12 months, and whenever a change in the worker's face could affect the fit, under 29 CFR 1910.134(f).
What is the assigned protection factor of a half-mask respirator?
Ten, for a filtering facepiece or elastomeric half-mask air-purifying respirator.
How do you calculate maximum use concentration?
Multiply the respirator's assigned protection factor by the exposure limit of the contaminant. Never use an air-purifying respirator at or above IDLH.
This guide summarizes federal OSHA, Cal/OSHA and EPA rules for training purposes. It is not legal advice. Always check the current regulation text and your site safety and health plan.