Assigned protection factor (APF)
How much protection a class of respirator is expected to give inside a working respiratory protection program.
Definition, in the source's words
29 CFR 1910.134(b)(opens ecfr.gov in a new tab)“Assigned protection factor (APF) means the workplace level of respiratory protection that a respirator or class of respirators is expected to provide to employees when the employer implements a continuing, effective respiratory protection program as specified by this section.”
What it means
APFs come from Table 1 in 1910.134(d)(3)(i)(A). A few to know: half mask air-purifying 10, full facepiece air-purifying 50, loose-fitting PAPR 25, pressure demand SCBA with a full facepiece 10,000.
An APF holds only inside a working program: fit testing, training, maintenance and medical evaluation.
Example
Air sampling shows 300 ppm of a vapor with a 50 ppm PEL. 300 ÷ 50 = 6 times the PEL, so the respirator needs an APF of at least 6. A half mask (APF 10) is enough on protection factor alone, if the cartridge suits the vapor.
Where it appears on the exam
ASP: ASP11 Domain 6, Industrial Hygiene and Occupational Health
Practice: Respiratory Protection
CSP: CSP11 Domain 3, Risk Management
Practice: PPE Hazard Assessment and Selection
Questions
- What is the APF of a half mask respirator?
- 10, in Table 1 of 1910.134(d)(3)(i)(A).
Related
- Maximum use concentration (MUC)
- Fit test
- IDLH (immediately dangerous to life or health)
- Regulation: 29 CFR 1910.134
Checked 2026-10-16. Spot a problem? Email hello@passcited.com.