Respirator guide
APR vs PAPR vs SCBA
Respirators fall into three families. The right one depends on the contaminant, its concentration relative to the exposure limit, and whether the atmosphere is IDLH or oxygen-deficient.
Air-Purifying Respirator (APR)
APF 5 – 50How it works: Filters or chemical cartridges clean the ambient air as you breathe. Includes N95 filtering facepieces, elastomeric half masks, and full-facepiece respirators.
When to use: A known contaminant, below the IDLH, in an atmosphere with adequate oxygen (≥19.5%). Needs the right filter/cartridge for the hazard.
Powered Air-Purifying Respirator (PAPR)
APF 25 – 1,000How it works: A battery-powered blower pulls air through filters and delivers it to the facepiece, helmet, or hood under slight positive pressure.
When to use: Higher protection and comfort than an APR; loose-fitting hoods work for users with facial hair. Still not for IDLH or oxygen-deficient atmospheres.
Supplied-Air / SCBA
APF up to 10,000How it works: Atmosphere-supplying respirators deliver clean breathing air from an airline (SAR) or a carried cylinder (SCBA), independent of the surrounding air.
When to use: Required for IDLH atmospheres, oxygen deficiency, and very high concentrations. A full-facepiece pressure-demand SCBA (APF 10,000) is the highest-protection option.
How to choose
Start with the hazard ratio — the measured concentration divided by the exposure limit. The respirator’s assigned protection factor must meet or exceed it. Among adequate options, choose the least over-protective one that fits your work, filter needs, and comfort requirements. If the concentration reaches the IDLH, only a full-facepiece pressure-demand SCBA (or a full-facepiece pressure-demand supplied-air respirator with auxiliary SCBA) may be used.
See the full APF table on how it works, or run your numbers in the calculator. Reference only — verify with a qualified professional.