Respirator selection · particulate
Particulates not otherwise regulated (PNOR) respirator selection— (catch-all for inert dusts without a specific standard)
Default category for inert/nuisance mineral, inorganic and organic dusts lacking a specific PEL - e.g., limestone/calcium carbonate, marble, gypsum, cellulose, Portland-cement-type dusts, and many other bulk dusts.
OSHA standard: 29 CFR 1910.1000, Table Z-1 ('Particulates not otherwise regulated (total)' and 'respirable fraction')
Particulate hazard. Measured in mg/m³ and captured by N/R/P particulate filters — not gas/vapor cartridges. Solid nuisance particulate, non-oil - N-series is sufficient; N95 minimum. Upgrade to N100/P100 for high dust loading, comfort, or where the specific dust later proves to have a more hazardous constituent. Not a gas/vapor hazard, so no chemical cartridge is required. See the cartridge & filter guide.
Calculator for Particulates not otherwise regulated (PNOR)
Result
Enter a concentration and an exposure limit to see the
compliant respirators and their Maximum Use Concentration.
Hazard ratio = concentration ÷ OEL · Minimum APF must meet or exceed it · MUC = APF × OEL (capped at IDLH). Source: OSHA 29 CFR 1910.134(d)(3)(i)(A), Table 1 — Assigned Protection Factors. Last verified 2026-07-16.
Maximum use concentration for Particulates not otherwise regulated (PNOR) by respirator
MUC = APF × the OSHA PEL (15 mg/m3) (no IDLH cap — none established). Use this as a reference for the highest concentration each respirator class may be used at.
| Respirator | APF | MUC (mg/m3) |
|---|---|---|
| Air-Purifying Respirator · Quarter mask | 5 | 75 |
| Air-Purifying Respirator · Half mask | 10 | 150 |
| Supplied-Air Respirator (Airline) · Half mask · Demand | 10 | 150 |
| Self-Contained Breathing Apparatus · Half mask · Demand | 10 | 150 |
| Powered Air-Purifying Respirator · Helmet / hood | 25 | 375 |
| Powered Air-Purifying Respirator · Loose-fitting facepiece | 25 | 375 |
| Supplied-Air Respirator (Airline) · Helmet / hood · Continuous flow | 25 | 375 |
| Supplied-Air Respirator (Airline) · Loose-fitting facepiece · Continuous flow | 25 | 375 |
| Air-Purifying Respirator · Full facepiece | 50 | 750 |
| Powered Air-Purifying Respirator · Half mask | 50 | 750 |
| Supplied-Air Respirator (Airline) · Full facepiece · Demand | 50 | 750 |
| Supplied-Air Respirator (Airline) · Half mask · Continuous flow | 50 | 750 |
| Supplied-Air Respirator (Airline) · Half mask · Pressure-demand / positive-pressure | 50 | 750 |
| Self-Contained Breathing Apparatus · Full facepiece · Demand | 50 | 750 |
| Powered Air-Purifying Respirator · Full facepiece | 1,000 | 15,000 |
| Supplied-Air Respirator (Airline) · Full facepiece · Continuous flow | 1,000 | 15,000 |
| Supplied-Air Respirator (Airline) · Full facepiece · Pressure-demand / positive-pressure | 1,000 | 15,000 |
| Self-Contained Breathing Apparatus · Full facepiece · Pressure-demand / positive-pressure | 10,000 | 150,000 |
Notes
PNOR is a fallback for solid particulates that have no substance-specific standard; it is equivalent to the older 'inert or nuisance dust' limit. If a dust is later identified as a regulated substance (silica, lead, etc.), the substance-specific PEL supersedes PNOR. NIOSH does not publish a numeric REL for the PNOR category, and no IDLH is defined.
Sources
- https://www.osha.gov/chemicaldata/801
- https://www.osha.gov/annotated-pels/table-z-1
- https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1000TABLEZ1
Data confidence: high. Values are cited from OSHA and NIOSH but should be verified against the current source and a qualified professional before use. See how this works.