History of U.S. Respirator Approval (Continued) Particulate Respirators.

This is the final article in a series of four articles on respirator history. This article continues to follow the history of respirator approval, use, and improvements in the U.S. as discussed in our article entitled, History of U.S. Respirator Approval, published in the ISRP Journal, Vol. 35, No. 1, 2018 (Spelce et al., 2018). This article is entirely about the history of respirators for protection against particulate hazards since the most extensive records available for the United States Bureau of Mines (USBM) approval schedules are for dust/fume/mist respirators.