History of U.S. Respirator Approval (Continued) - Gas masks, Supplied-air respirators, and Chemical cartridge respirators.

This article is the third in a series of four articles on respirator history. This article continues to follow the history of respirator approval, use, and improvements in the US as discussed in our article entitled, , published in the ISRP Journal, Vol. 35, No. 1, 2018 (Spelce. et. al.2018). In addition, a 1957 respirator decision logic diagram illustrates the U.S. Bureau of Mines (USBM) rules to follow for respirator selection (USBM 1957).