OSHA term · Glossary
Filtering Facepiece Respirator (N95)
Verified vs OSHA sources · 2026-10-05
A disposable, tight-fitting air-purifying respirator in which the entire facepiece is the filter — most familiarly the N95. It filters airborne particles but provides NO protection against gases, vapors, or oxygen-deficient atmospheres. NIOSH certifies particulate filters under 42 CFR Part 84 by oil resistance (N = Restricted to workplaces free of oil aerosols, R = Intended for particulates that include oil-based liquids, P = Also intended for oil-based particulates; the usual mnemonic reads P as oil-proof) and efficiency (95 = ≥ 95%, 99 = ≥ 99%, 100 = ≥ 99.97% (HEPA-equivalent, 29 CFR 1910.134(b))), giving nine classes. As a tight-fitting respirator it has an assigned protection factor of 10 and, when used to comply with OSHA requirements, needs fit testing, medical evaluation, and a written program.
Also known as: N95, FFR, disposable respirator, particulate respirator
On this page
Filtering Facepiece Respirator (N95) at a glance
- NIOSH 42 CFR 84 classes: three series (N/R/P) × three efficiencies (95/99/100) = nine classes (N95, N99, N100, R95, R99, R100, P95, P99, P100).
- N = Restricted to workplaces free of oil aerosols (42 CFR 84.170(a)(2)); R = Intended for particulates that include oil-based liquids (42 CFR 84.170(a)(2)); P = Also intended for oil-based particulates; the usual mnemonic reads P as oil-proof.
- Efficiency measured under 42 CFR 84.181 with a solid sodium chloride aerosol (count median diameter 0.075 µm) (N series) or a liquid DOP aerosol (count median diameter 0.185 µm) (R and P series) at 85 L/min: 95 = ≥ 95%, 99 = ≥ 99%, 100 = ≥ 99.97% (HEPA-equivalent, 29 CFR 1910.134(b)).
- Assigned protection factor: 10 (it is a tight-fitting half-mask respirator).
- Protects against PARTICLES only — not gases, vapors, or oxygen-deficient/IDLH atmospheres.
- When required by OSHA, it needs fit testing, medical evaluation, and a written program — same as any tight-fitting respirator.
- Voluntary use of a filtering facepiece still requires the employer to provide Appendix D information (but not a full program).
In plain English
The familiar disposable dust/particle mask where the whole mask is the filter — the N95 being the best-known. It stops fine particles (dusts, mists, some bioaerosols) but does nothing against gases, vapors, or lack of oxygen. The 'N' means not oil-resistant and '95' means it captures at least 95% of test particles. Even a disposable N95 needs fit testing and a medical evaluation when required for OSHA compliance.
What the rule says
“Filtering facepiece (dust mask) means a negative pressure particulate respirator with a filter as an integral part of the facepiece or with the entire facepiece composed of the filtering medium.”
In context
An enforcement, recordkeeping, or general-duty concept under the Occupational Safety and Health Act and 29 CFR. These terms define how OSHA inspects, cites, and penalizes employers.
Where this is written in OSHA's rules
- 29 CFR 1910.134Read on eCFR / OSHA.gov
- 29 CFR 1910.134(b)Read on eCFR / OSHA.gov
Example
A drywall finisher sanding joint compound is exposed to nuisance and respirable dust below 10× the applicable limit. An N95 filtering facepiece (APF 10) is an appropriate particulate respirator for this task. Because the exposure is particulate (no oil aerosol, no vapor), the 'N' series is suitable and 95% efficiency is adequate. The employer still must medically clear the worker, fit test the specific N95 model, and run a written respiratory protection program. If the same worker later sprayed a solvent-based coating (vapor hazard), the N95 would be useless and a chemical-cartridge respirator would be required.
Why it matters
The N95 is the most widely used respirator in the world, and its very familiarity breeds dangerous misuse. It protects only against particles — workers who wear one against solvent vapors, welding gases, or in low-oxygen spaces are unprotected. And because it is a tight-fitting respirator, an N95 required for the job carries the same fit-testing, medical-evaluation, and program obligations as any half mask; treating it as 'just a dust mask' is a common and citable compliance gap.
N95 vs. P100 — and why 'N' matters
The letter is about oil, not overall quality. An N-series filter (like N95) is Not resistant to oil aerosols and must not be used where oil mists are present; an R-series is Resistant for up to 8 hours; a P-series (like P100) is oil-Proof. The number is efficiency: 95%, 99%, or 99.97% (100). So a P100 both resists oil and filters ≥99.97% of particles, while an N95 filters ≥95% but only in oil-free atmospheres. Choosing between them depends on the presence of oil aerosols and the efficiency needed — not on a vague sense that 'higher is always better.' None of them protect against gases or vapors.
NIOSH 42 CFR 84 Particulate Filter Classes
| Series (oil resistance) | 95% | 99% | 99.97% (100) |
|---|---|---|---|
| N — not oil resistant | N95 | N99 | N100 |
| R — oil resistant (≤ 8 hr) | R95 | R99 | R100 |
| P — oil proof | P95 | P99 | P100 |
Filtering Facepiece Respirator (N95): frequently asked questions
- What does N95 mean?
- N95 is a NIOSH filter classification under 42 CFR Part 84. The 'N' means the filter is Not resistant to oil (it must only be used where no oil aerosols are present), and '95' means a minimum filter efficiency of ≥ 95% in NIOSH's test (42 CFR 84.181). An N95 filtering facepiece is a tight-fitting half-mask respirator with an assigned protection factor of 10, and it protects only against particles — not gases, vapors, or low oxygen.
- Does an N95 need fit testing and a medical evaluation?
- Yes, when it is required for the job under OSHA. An N95 is a tight-fitting respirator, so its use to comply with OSHA requirements triggers the full 1910.134 program: medical evaluation before use, annual fit testing on the specific model, training, and a written program. Only truly VOLUNTARY filtering-facepiece use is relieved of fit testing and the full program — but even then the employer must provide the Appendix D information and ensure voluntary use does not itself create a hazard.
- What is the difference between N95, R95, and P95?
- All three filter at least ≥ 95% of particles; they differ only in oil resistance. N95 is Not resistant to oil and must be used only in oil-free atmospheres. R95 and P95 are both intended for particulates that include oil-based liquids (42 CFR 84.170(a)(2)); with oil present, follow the manufacturer's time-use instructions. If oil aerosols may be present, an R- or P-series filter is required; where no oil is present, an N-series is acceptable.
Related terms
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More OSHA terms
The action an employer takes to fix a cited violation or eliminate a hazard OSHA identified during an inspection. The citation sets an abatement date, the deadline to correct the hazard, and within 10 calendar days after that date the employer must certify to OSHA that the violation was abated. Failure to abate accrues additional penalties of up to $16,550 per day.
Area DirectorThe senior OSHA official in charge of a specific OSHA Area Office — the local unit that runs inspections and enforcement in its geographic territory. The Area Director has the authority to issue citations, propose penalties, hold informal conferences with employers, and approve settlement agreements. When a Compliance Safety and Health Officer (CSHO) completes an inspection, it's the Area Director who ultimately issues the citation.
Bureau of Labor Statistics (BLS)The federal statistical agency within the U.S. Department of Labor that collects, analyzes, and publishes data on workplace injuries, illnesses, and fatalities. BLS conducts the annual Survey of Occupational Injuries and Illnesses (SOII) — compiled from employer OSHA 300 logs — and the Census of Fatal Occupational Injuries (CFOI). SOII data drives OSHA's Site-Specific Targeting (SST) program: establishments whose DART rates significantly exceed their BLS industry average are placed on the SST inspection list.
Competent PersonUnder OSHA's construction standards, a person who is capable of identifying existing and predictable hazards in the surroundings or working conditions, and who has the authorization to take prompt corrective measures to eliminate them. The role requires both knowledge and the authority to act, and is mandated by name in many specific standards — excavations, scaffolds, fall protection, asbestos, and more.
CitationThe formal written notice OSHA issues to an employer after an inspection, describing each alleged violation, the standard cited, the proposed penalty, and the date by which the hazard must be corrected (abated). OSHA must issue a citation with reasonable promptness and no later than six months after the violation occurred.
Closing ConferenceThe meeting at the end of an OSHA inspection where the compliance officer confers with the employer and informally advises them of any apparent violations found. Importantly, the closing conference discusses what was observed and the employer's rights — but it does NOT state final citations or penalties, which come later in the written Citation and Notification of Penalty.
Compliance Officer (CSHO)An OSHA Compliance Safety and Health Officer — the inspector who conducts workplace inspections. A CSHO presents credentials (a photo ID and a serial number), holds the opening conference, performs the walkaround, collects evidence, interviews employees, and recommends citations. CSHOs are either safety specialists or industrial hygienists.
ContestAn employer's formal challenge to an OSHA citation, penalty, or abatement date. To contest, the employer must file a written Notice of Contest with the OSHA Area Director within 15 working days of receiving the Citation and Notification of Penalty. Filing sends the case to the independent Occupational Safety and Health Review Commission (OSHRC); missing the deadline makes the citation a final, un-appealable order.
Sources & verification
- 29 CFR 1910.134 (eCFR / OSHA.gov)
- 29 CFR 1910.134(b) (eCFR / OSHA.gov)
- NIOSH — Respirator Types and Approvals (NPPTL)
- OSHA — 29 CFR 1910.134 (Respiratory Protection)
Reviewed by HazComFast against eCFR, OSHA.gov, NIOSH, and the Federal Register. Last reviewed 2026-10-05. This glossary is general information, not legal advice; OSHA State-Plan states (e.g. California, Michigan) may adopt stricter requirements.
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