The selection of a respirator can be confusing, but if we keep just four (4) things in mind we can at least determine if we can use an Air-Purifying Respirator (APR). These four things are:
- The chemical/particulate we need to protect us from
- The concentration of that chemical/particulate
- The IDLH of said chemical/particulate AND that our concentration is BELOW the IDLH
- There is ample oxygen available (>19.5%)
If we do not know ALL four (4) of these pieces of data, we are in an “unknown atmosphere” and in this type of atmosphere we MUST use either:
- A full facepiece pressure demand SCBA certified by NIOSH for a minimum service life of thirty minutes, or
- A combination full facepiece pressure demand supplied-air respirator (SAR) with auxiliary self-contained air supply
Sources:
1910.134(d)(3)(i)(A) Assigned Protection Factors (APFs) Employers must use the assigned protection factors listed in Table 1 to select a respirator that meets or exceeds the required level of employee protection.
1910.134(d)(3)(i)(B)(1) The employer must select a respirator for employee use that maintains the employee’s exposure to the hazardous substance, when measured outside the respirator, at or below the MUC.
1910.134(d)(3)(i)(B)(2)
Employers must not apply MUCs to conditions that are immediately dangerous to life or health (IDLH); instead, they must use respirators listed for IDLH conditions in paragraph (d)(2) of this standard.
1910.134(d)(3)(ii) The respirator selected shall be appropriate for the chemical state and physical form of the contaminant.
Oxygen deficient atmosphere means an atmosphere with an oxygen content below 19.5% by volume.