Respirator guide
Cartridge & filter selection
The respirator class sets the assigned protection factor; the cartridge or filter determines what it protects against. They are separate choices.
Particulates vs gases & vapors
This is the first fork. Particulate filters (the N/R/P series) capture dusts, mists, fumes, and bioaerosols — but do nothing for gases or vapors. Gas and vapor cartridges use sorbents matched to a specific chemical family. If a hazard has both a particulate and a vapor component, use a combination cartridge.
Common filter and cartridge types
| Type | Protects against | Notes |
|---|---|---|
| N95 / N99 / N100 | Non-oil particulates only | Filtering facepieces or cartridges; the number is % efficiency. Not oil-resistant. |
| R95 | Particulates incl. some oil-based | Oil-resistant up to 8 hours. |
| P95 / P100 | Particulates incl. oil | Oil-proof. P100 (often magenta) is the highest particulate class. |
| Organic Vapor (OV) | Solvent vapors | Black band. For substances like toluene, acetone, MEK. |
| Acid Gas (AG) | Chlorine, HCl, SO₂, etc. | White band. |
| Ammonia / Methylamine | Ammonia | Green band. |
| Formaldehyde | Formaldehyde | Dedicated cartridge; OV cartridges are not reliable for formaldehyde. |
| Multi-gas / combination | Mixed hazards + particulates | OV/AG plus a P100 pre-filter. |
Change-out schedule (gas & vapor)
OSHA 29 CFR 1910.134(d)(3) prohibits relying on taste or smell to know when a gas/vapor cartridge is spent. Employers must establish a cartridge change schedule based on objective information — a manufacturer’s software model (based on the chemical, concentration, humidity, and work rate) or an end-of-service-life indicator (ESLI). Particulate filters are typically changed on increased breathing resistance or damage.
Related
Pick the respirator class and concentration limit with the calculator, review the N95 particulate case in the N95 guide, and see the substance list for hazard-specific notes under substances. Reference only — verify with the cartridge manufacturer and a qualified professional.