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A PAPR hood is the loose head covering of a powered air-purifying respirator (PAPR): a blower pulls room air through filters and delivers it into a hood that covers the head and neck. It is used by people who need respiratory protection against airborne particles and who work under a written respiratory protection program. This page covers the hood, its filters and its protection factor; for the PAPR versus N95 decision see PAPR vs N95 for research labs.
This page describes products and general use; it is not medical advice.
What a PAPR hood is
OSHA’s respiratory protection standard (29 CFR 1910.134) defines a hood as a respiratory inlet covering that completely covers the head and neck and may also cover portions of the shoulders and torso. A PAPR is the powered type of air-purifying respirator, so the hood is the part you see and the blower and filters supply the air. People who use PAPR hoods include laboratory staff and other workers covered by an employer’s respiratory protection program.
How a PAPR assembly is built
The standard names the parts of the system that matter for protection: the respiratory inlet covering (a facepiece, helmet, hood, suit or mouthpiece), and the air-purifying device that cleans the air. In a PAPR the air-purifying device is a powered unit with filters, connected to the inlet covering so that clean air flows into it. The hood therefore does not filter anything itself; it is the delivery surface for filtered air.
Hood, helmet and tight-fitting types
1910.134 uses separate definitions for the coverings a PAPR can use. A helmet is a rigid inlet covering that also protects the head against impact and penetration. A loose-fitting facepiece is designed to form only a partial seal with the face. A hood covers the whole head and neck. The assigned protection factor (APF) for each PAPR covering in the standard’s Table 1 is below.
| PAPR covering | APF in 29 CFR 1910.134 Table 1 | Fit test under the standard | Filter test airflow (42 CFR 84.175) |
|---|---|---|---|
| Half mask (tight-fitting) | 50 | Required (tight-fitting) | 115 L/min |
| Full facepiece (tight-fitting) | 1,000 | Required (tight-fitting) | 115 L/min |
| Helmet or hood | 25, or 1,000 only with manufacturer evidence (footnote 4) | Not required by the tight-fitting rule | 170 L/min (loose-fitting inlet coverings) |
| Loose-fitting facepiece | 25 | Not required by the tight-fitting rule | 170 L/min |
The fit-test column reflects paragraph (f)(1), which requires a fit test for employees using a tight-fitting facepiece respirator. Sources are listed at the end of this page.
The hood APF rule: 25 or 1,000
Table 1 lists helmet or hood PAPRs as 25/1,000. Footnote 4 explains the split: the employer must have evidence provided by the respirator manufacturer that testing demonstrates performance at a protection level of 1,000 or greater to use an APF of 1,000. Absent such testing, all other PAPRs and supplied-air respirators with helmets or hoods are to be treated as loose-fitting facepiece respirators, with an APF of 25. See respirator levels and protection factors for how APF compares across respirator types.
PAPR filters
Particulate filters for powered respirators are certified under 42 CFR Part 84. Section 84.175 tests powered air-purifying particulate respirators with a DOP aerosol at 100 mg/m3 for 5 to 10 seconds, and the filter’s total efficiency must be at least 99.97 percent. The test flow differs by covering: 115 liters per minute for tight-fitting inlet coverings and 170 liters per minute for loose-fitting ones. A unit with several filters is tested by dividing the flow by the number of filters.
How to choose
Three points from the standard guide the choice. First, the APF must be high enough for the exposure the employer’s program has assessed; a hood without manufacturer testing evidence is limited to APF 25. Second, whether a fit test is needed depends on whether the covering is tight-fitting; see respirator fit testing requirements. Third, selection sits inside a written program; see respiratory protection program for laboratories.
Safe use and handling basics
Paragraph (h)(3)(i) of 1910.134 requires respirators used in routine situations to be inspected before each use and during cleaning. Follow the manufacturer’s instructions for the specific hood, blower and filter, and the employer’s respiratory protection program for training, cleaning and storage. Employees who are required to wear a respirator also fall under the program’s medical evaluation process; see the respirator medical clearance questionnaire guide.
Common mistakes
- Assuming every hood carries APF 1,000. Without manufacturer testing evidence the standard treats a PAPR hood as APF 25.
- Assuming no fit test means no program. The fit-test rule is worded for tight-fitting facepieces; the training, inspection and other program duties still apply.
- Skipping the pre-use inspection that paragraph (h)(3)(i) requires for routine-use respirators.
FAQ
What is a PAPR hood?
It is the loose-fitting head and neck covering of a powered air-purifying respirator, which receives filtered air from a blower unit.
Do PAPR filters need replacing on a schedule?
The change-schedule rule in 1910.134(d)(3)(iii)(B)(2) is for gas and vapor cartridges without an end-of-service-life indicator, not particulate filters. For particulate filters, follow the manufacturer’s instructions for the model.
PAPR vs N95: which gives more protection?
Under Table 1 a filtering facepiece falls in the APF 10 category and a hood PAPR has 25 (or 1,000 with manufacturer evidence). The full comparison is in PAPR vs N95 for research labs.
Are PAPRs used in healthcare?
The OSHA and 42 CFR 84 rules described here apply to PAPR hoods in any workplace that requires respirators. Setting-specific guidance should come from the employer’s respiratory protection program and the manufacturer’s instructions.
Sources
- OSHA, 29 CFR 1910.134, Respiratory protection: https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134 (definitions, Table 1 and footnote 4, paragraphs (d)(3)(iii)(B)(2), (f)(1), (h)(3)(i)). Text checked 2026-10-30 at https://www.law.cornell.edu/cfr/text/29/1910.134.
- 42 CFR 84.175, Airflow resistance and filter tests for powered air-purifying particulate respirators: https://www.law.cornell.edu/cfr/text/42/84.175. Checked 2026-10-30.
