Respirator selection
Nitrogen dioxide respirator selectionNO2
Welding and combustion/diesel-exhaust environments, silo/agriculture (silo gas), and nitric acid/explosives manufacturing.
These are federal OSHA limits. The PEL shown is the federal OSHA value. About two dozen states run their own OSHA-approved plans, and some — notably California (Cal/OSHA) — enforce lower or additional exposure limits. If you work under a state plan, check your state's PEL and enter it as a custom limit in the calculator.
Cartridge (limited use): Acid Gas (AG) canister — ESCAPE ONLY; supplied-air/SCBA for work exposure — White band
An APR fitted with the correct cartridge is only adequate up to its MUC (below) — the cartridge must be able to capture nitrogen dioxide. APR is NOT permitted for routine work exposure — NIOSH lists only supplied-air/SCBA for protection and allows an air-purifying gas-mask canister for ESCAPE ONLY. NO2 has poor warning properties and a low IDLH; cartridges are unreliable for it. Use supplied air or SCBA for any work in NO2. You must establish a change-out schedule; never rely on taste or smell. See the cartridge & filter guide.
The OSHA limit for nitrogen dioxide is a ceiling value, not an 8-hour average. The MUC method below is defined for time-weighted limits, so apply professional judgment.
Calculator for Nitrogen dioxide
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 Nitrogen dioxide by respirator
MUC = APF × the OSHA PEL (5 ppm), capped at the IDLH (13 ppm). Use this as a reference for the highest concentration each respirator class may be used at.
| Respirator | APF | MUC (ppm) |
|---|---|---|
| Air-Purifying Respirator · Quarter mask | 5 | 13IDLH |
| Air-Purifying Respirator · Half mask | 10 | 13IDLH |
| Supplied-Air Respirator (Airline) · Half mask · Demand | 10 | 13IDLH |
| Self-Contained Breathing Apparatus · Half mask · Demand | 10 | 13IDLH |
| Powered Air-Purifying Respirator · Helmet / hood | 25 | 13IDLH |
| Powered Air-Purifying Respirator · Loose-fitting facepiece | 25 | 13IDLH |
| Supplied-Air Respirator (Airline) · Helmet / hood · Continuous flow | 25 | 13IDLH |
| Supplied-Air Respirator (Airline) · Loose-fitting facepiece · Continuous flow | 25 | 13IDLH |
| Air-Purifying Respirator · Full facepiece | 50 | 13IDLH |
| Powered Air-Purifying Respirator · Half mask | 50 | 13IDLH |
| Supplied-Air Respirator (Airline) · Full facepiece · Demand | 50 | 13IDLH |
| Supplied-Air Respirator (Airline) · Half mask · Continuous flow | 50 | 13IDLH |
| Supplied-Air Respirator (Airline) · Half mask · Pressure-demand / positive-pressure | 50 | 13IDLH |
| Self-Contained Breathing Apparatus · Full facepiece · Demand | 50 | 13IDLH |
| Powered Air-Purifying Respirator · Full facepiece | 1,000 | 13IDLH |
| Supplied-Air Respirator (Airline) · Full facepiece · Continuous flow | 1,000 | 13IDLH |
| Supplied-Air Respirator (Airline) · Full facepiece · Pressure-demand / positive-pressure | 1,000 | 13IDLH |
| Self-Contained Breathing Apparatus · Full facepiece · Pressure-demand / positive-pressure | 10,000 | 13IDLH |
Notes
NIOSH REL STEL 1 ppm; NIOSH sets no 8-hr TWA. OSHA PEL Ceiling 5 ppm (Table Z-1). IDLH revised to 13 ppm (NPG cites 2017-202; older 20 ppm superseded). NPG conversion 1 ppm = 1.88 mg/m3; MW 46.0.
Sources
- https://www.cdc.gov/niosh/npg/npgd0454.html
- https://www.cdc.gov/niosh/idlh/10102440.html
- https://www.osha.gov/annotated-pels/table-z-1
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.