Written and maintained by CASRAI Editorial Board
Last updated
General product information only, not medical advice. Respirator selection for a workplace is an employer responsibility under OSHA’s respiratory protection standard.
Overview: what a half face respirator is
A half face respirator (an elastomeric half mask respirator, or EHMR) is a reusable, tight-fitting respirator that covers the nose and mouth and takes exchangeable filters or cartridges. NIOSH describes the facepiece as synthetic or natural rubber, which is what allows repeated cleaning, disinfection, storage and reuse. Because it must seal to the face, it needs a fit test (OSHA respirator fit test). What it protects against depends on the filter or cartridge fitted, not the facepiece.
Under 29 CFR 1910.134 Table 1, an air-purifying half mask (the footnote includes filtering facepieces and half masks with elastomeric facepieces) has an assigned protection factor of 10; a powered air-purifying half mask is 50. See respirator levels for the full table.
Types table
| Type | What it is | Best for | Limits |
|---|---|---|---|
| Elastomeric half mask, particulate filters | Rubber facepiece with exchangeable particulate filters; may have no exhalation valve | Particles only; same nine particulate filter classes as filtering facepieces | Without an exhalation valve it is approved only for particulate filters and cannot take gas or vapor cartridges |
| Elastomeric half mask, gas/vapor cartridges | Rubber facepiece with chemical cartridges, optionally combined with particulate filters | Gases and vapors, when the cartridge is certified for the contaminant | Must have functional inhalation and exhalation valves, which protect the cartridge from moisture in exhaled air |
| Filtering facepiece | OSHA: a negative pressure particulate respirator with a filter as an integral part of the facepiece | Particles; also assigned protection factor 10 | Filter is part of the facepiece rather than exchangeable; see what is an N95 respirator |
| Powered air-purifying half mask | Half-mask facepiece supplied with filtered air by a blower | Higher assigned protection factor (50) | Needs a powered unit; see PAPR hood for the powered category |
| Full facepiece | Covers the whole face | Different category with its own protection factor | See full face respirator |
NIOSH states that an EHMR offers at least equivalent or greater protection than an N95 filtering facepiece respirator, and notes limits: it may interfere with communication and downward gaze, it must be stored between shifts, and it needs cleaning and disinfecting.
Half face respirator vs N95
Both are negative pressure, tight-fitting particulate options with the same assigned protection factor (10) in OSHA Table 1. The practical difference is that the half face respirator is reusable with replaceable filters or cartridges, and can carry chemical cartridges when it has the required valves; an N95 cannot.
Half face respirator for chemical fumes
Particulate filters stop particles, not gases or vapors. For gases and vapors, OSHA 1910.134(d)(3)(iii) requires either a cartridge with an end-of-service-life indicator (ESLI) certified by NIOSH for the contaminant, or a cartridge change schedule based on objective information or data. CDC’s archived oil-spill guidance describes a combination organic vapor/P100 cartridge as protecting against both particulates and gases/vapors (see respirator cartridges).
How to choose by setting
The sources do not rank settings; they set rules that apply wherever a tight-fitting respirator is used at work.
- Any workplace, including laboratories: the employer must select a NIOSH-certified respirator (1910.134(d)(1)(ii)) and run a program; for bench work see respiratory protection program for laboratories and respirator medical clearance.
- Healthcare: NIOSH says the exhalation valve should be considered before use in a sterile setting or as source control (see exhalation valve).
What to check on the label
| Marking | Meaning (42 CFR 84.179) |
|---|---|
| N95, R95, P95 | 95% filter efficiency level; not magenta |
| N100, R100 | 99.97% filter efficiency level; any colour except magenta |
| P100 | “P100 Particulate Filter (99.97% filter efficiency level)”; colour-coded magenta |
The letter is the series (N, R or P) and the number is the efficiency level, specified by the manufacturer at certification. Check for a NIOSH approval label: NIOSH has reported a trend towards fraudulent respirator components such as filters and cartridges, so confirm approval against the NIOSH Certified Equipment List.
Care and replacement
- Fit test: before initial use, whenever a different facepiece (size, style, model or make) is used, and at least annually (1910.134(f)(2)).
- Seal check: each time it is put on (1910.134(g)(1)(iii)). Facial hair that comes between the sealing surface and the face, or interferes with valve function, is a listed bar to tight-fitting facepiece use (g)(1)(i)(A).
- Inspection: before each use and during cleaning for routine-use respirators (h)(3)(i)(A).
- Cleaning: a respirator issued to more than one person must be cleaned and disinfected before a different person wears it (h)(1)(ii). NIOSH advises following the manufacturer’s cleaning guidelines first.
- Storage: protect from damage, contamination, dust, sunlight and extreme temperatures (h)(2)(i).
- Cartridges: use an ESLI or a change schedule, as above.
FAQ
Does a half face respirator protect against chemical fumes?
Only with a gas or vapor cartridge certified for that contaminant, on a facepiece with the required valves, under a change schedule or ESLI. Particulate filters do not stop vapors.
Is a half face respirator the same as a full face respirator?
No. A full facepiece covers the whole face and is a separate category; see full face respirator.
Is a P100 half face respirator better than N95?
P100 is a 99.97% efficiency level and N95 a 95% level under 42 CFR 84.179. The assigned protection factor for an air-purifying half mask is 10 either way.
Does it need a fit test?
Yes. NIOSH says EHMRs need fit testing because they must seal tightly, and OSHA requires it before initial use and at least annually.
Sources
- OSHA, 29 CFR 1910.134 Respiratory protection, read 2026-11-07.
- CDC PPE-Info, 42 CFR 84.179 Filter efficiency levels, read 2026-11-07.
- NIOSH, Elastomeric Respirators, read 2026-11-07.
- NIOSH, Performance Testing of Fraudulent Respirator P100 case report (2025), read 2026-11-07.
- CDC, Oil Spill Response: Use of Respiratory Protection (archived), read 2026-11-07.
