4.https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.252#
“Numerous Questions on Filtering Facepiece/Dusk Mask Respirators. | Occupational Safety and Health Administration.” n.d. Accessed August 12, 2020.https://www.osha.gov/laws-regs/standardinterpretations/2011-11-22-0. “Qualitative Fit Testing - Quick Tips #324 - Grainger...