Respirator selection
Nitric acid respirator selectionHNO3
Fertilizer (ammonium nitrate) and explosives manufacture, metal etching/pickling, electronics, and oxidizer production.
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.
Recommended cartridge: Acid Gas (AG) — full facepiece — White band
An APR fitted with the correct cartridge is only adequate up to its MUC (below) — the cartridge must be able to capture nitric acid. Full-facepiece acid-gas CCR is NIOSH-listed up to the 25 ppm IDLH, but nitric acid is a strong oxidizer/corrosive whose vapors co-occur with NO2 — and NO2 is NOT reliably cartridge-removable. Evaluate the full atmosphere; if NO2 is present use supplied air/SCBA. Above IDLH supplied air/SCBA required. You must establish a change-out schedule; never rely on taste or smell. See the cartridge & filter guide.
Calculator for Nitric acid
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 Nitric acid by respirator
MUC = APF × the OSHA PEL (2 ppm), capped at the IDLH (25 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 | 10 |
| Air-Purifying Respirator · Half mask | 10 | 20 |
| Supplied-Air Respirator (Airline) · Half mask · Demand | 10 | 20 |
| Self-Contained Breathing Apparatus · Half mask · Demand | 10 | 20 |
| Powered Air-Purifying Respirator · Helmet / hood | 25 | 25IDLH |
| Powered Air-Purifying Respirator · Loose-fitting facepiece | 25 | 25IDLH |
| Supplied-Air Respirator (Airline) · Helmet / hood · Continuous flow | 25 | 25IDLH |
| Supplied-Air Respirator (Airline) · Loose-fitting facepiece · Continuous flow | 25 | 25IDLH |
| Air-Purifying Respirator · Full facepiece | 50 | 25IDLH |
| Powered Air-Purifying Respirator · Half mask | 50 | 25IDLH |
| Supplied-Air Respirator (Airline) · Full facepiece · Demand | 50 | 25IDLH |
| Supplied-Air Respirator (Airline) · Half mask · Continuous flow | 50 | 25IDLH |
| Supplied-Air Respirator (Airline) · Half mask · Pressure-demand / positive-pressure | 50 | 25IDLH |
| Self-Contained Breathing Apparatus · Full facepiece · Demand | 50 | 25IDLH |
| Powered Air-Purifying Respirator · Full facepiece | 1,000 | 25IDLH |
| Supplied-Air Respirator (Airline) · Full facepiece · Continuous flow | 1,000 | 25IDLH |
| Supplied-Air Respirator (Airline) · Full facepiece · Pressure-demand / positive-pressure | 1,000 | 25IDLH |
| Self-Contained Breathing Apparatus · Full facepiece · Pressure-demand / positive-pressure | 10,000 | 25IDLH |
Notes
NIOSH REL TWA 2 ppm (5 mg/m3) AND STEL 4 ppm (10 mg/m3). OSHA PEL TWA 2 ppm (5 mg/m3). IDLH 25 ppm. Conversion 1 ppm = 2.58 mg/m3; MW 63.0.
Sources
- https://www.cdc.gov/niosh/npg/npgd0447.html
- https://www.cdc.gov/niosh/idlh/7697372.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.