This Practice was withdrawn on May 11, 2007. A significant portion of this Practice was included in the 2004 ISA revision which has been accepted by ANSI, IEC, and OSHA. This Practice provides designers of Safety Instrumented Systems (SIS) with engineering guidelines appropriate for SIS meeting requirements as defined in ANSI/ISA-S84.01-1996, Application of Safety Instrumented Systems for the Process Industries (hereafter referred to as S84).This Practice provides information to supplement Sections 5, 6, and 7 and Appendix B of S84 regarding the specification and design of SIS. Installation, maintenance, and testing issues are addressed only to the extent required for incorporation during SIS design. The information in this Practice is presented in the form of additional examples and design considerations that should be considered by SIS designers.This Practice is not a standalone document and should be used in conjunction with S84. To facilitate cross-referencing, section numbers and titles in this Practice are followed by corresponding S84 section numbers enclosed in brackets ({ }).