Testing safety systems "on" and "off" line is not only a requirement of OSHA's PSM,but necessary to maintain the target safety integrity level (SIL) as defined by ANSI/ISA S84.01. This paper will discuss mandatory requirements for testing, facilities for testing and bypassing, what components need to be checked, bypassing the safety system, procedures for testing and bypassing, documentation for testing and bypassing, SIL Vs testing frequency, and justification for testing. The paper concludes with the most used bypassing philosophy with several recommendations for online bypassing facilities.