Respirator Selection Calculator
Determine the required OSHA Assigned Protection Factor (APF) and recommended respirator type from airborne concentration and occupational exposure limit.
Inputs
Results
Hazard ratio
10
How to Use This Calculator
- Enter Airborne concentration, OEL / PEL / TLV, and IDLH concentration.
- Set Oxygen level (%).
- Review the Hazard ratio result.
- Use Required APF and Effective MUC to inform your decision.
How the result changes with OEL / PEL / TLV
| OEL / PEL / TLV | Hazard ratio |
|---|---|
| 10,000 | 0.01 |
| 35,000 | 0 |
| 65,000 | 0 |
| 90,000 | 0 |
What each input means
- Airborne concentration
- Measured or estimated airborne concentration (ppm or mg/m³ — use same units as OEL).
- OEL / PEL / TLV
- Occupational Exposure Limit — the PEL, TLV, or REL for the substance (same units as concentration).
- IDLH concentration
- Immediately Dangerous to Life or Health concentration (0 if unknown). Same units.
- Oxygen level (%)
- Atmospheric oxygen percentage. Normal air = 20.9%. Below 19.5% is oxygen-deficient.
What each result means
- Hazard ratio
- Ratio of airborne concentration to the OEL. Values > 1 require respiratory protection.
- Required APF
- Minimum Assigned Protection Factor needed (OSHA 29 CFR 1910.134 Table 1 tier).
- Effective MUC
- Maximum Use Concentration for the selected respirator (capped at IDLH if specified).
- Respirator type code
- 0=half-mask APR, 1=loose PAPR, 2=full-face APR/PAPR, 3=SAR, 4=SCBA, 5=not feasible.
- O₂ deficient?
- 1 if oxygen < 19.5%, requiring supplied-air respirator.
- Protection margin
- APF headroom — how many times the required APF exceeds the hazard ratio.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersAirborne concentration = 100, OEL / PEL / TLV = 10, IDLH concentration = 500, Oxygen level (%) = 20.9 = 4 input(s) provided
- Calculate Hazard ratioHazard ratio = airborneConc / oel10 = 10
- Calculate Required APFRequired APF10 = 10
- Calculate Effective MUC100 = 100
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