The purpose of this respirator selection logic (RSL) is to provide a process that respirator program administrators can use to select appropriate respirators for the protection of workers in specific workplaces. It is not intended to be used for selection of respirators for protection against infectious diseases or chemical, biological, radiological or nuclear (CBRN) exposures associated with terrorism events. This RSL contains a series of questions regarding situations which may require the use of respirators. (See Respirator Selection Logic Sequence, page 5.) In answering these questions, the user of this selection logic is assisted in identifying specific classes of respirators, applicable restrictions, and the appropriate respirator selection table to use. When using one of the tables to identify a suitable class of respirators, the user must keep in mind the restrictions identified in the question section of this respirator selection logic. This RSL identifies the criteria necessary to determine the classes of respirators that will provide the minimum acceptable degree of protection for a chemical at a given concentration. Classes of respirators offering greater protection can usually be used in place of the minimum acceptable class of respirators. Respirator classes are consistent with respirator certification groupings as specified in 42 CFR 84. The recommendations in this RSL are based primarily on the physical, chemical, and toxicologic properties of the contaminant and on the limitations of each class of respirator, including filtration efficiency, air supply capability, and face seal characteristics and leakage. Thus, this selection logic is limited to identifying classes of acceptable respirators, rather than individual respirator models.