Work out respirator protection factor instantly with clear inputs, formula shown and shareable results.
The hazard ratio, ambient concentration divided by the exposure limit, is the minimum protection factor a respirator must provide. Assigned protection factors are 10 for a half mask, 50 for a full face with particulate filters, and 1000 or more for a powered or supplied air hood. The concentration inside the facepiece is ambient divided by the assigned factor.
Required protection
Required APF = ambient concentration / exposure limit
Inside concentration
Inside = ambient / assigned protection factor
Preliminary estimate only. Respiratory protection must be selected under a written programme with fit testing, medical clearance and cartridge change schedules as required by your regulator.
Required APF = ambient concentration / exposure limit. The hazard ratio, ambient concentration divided by the exposure limit, is the minimum protection factor a respirator must provide.
No. Above the immediately dangerous to life or health level, or in oxygen deficiency, no air purifying respirator is acceptable regardless of its factor: supplied air or self-contained breathing apparatus is required.
This calculator takes 3 inputs: Ambient concentration, Exposure limit, Assigned protection factor of the respirator. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.