The objective of this Standard is to provide information on - (a) the underlying concepts of risk and the relationship of risk to safety integrity (see Clause A.4); (b) the determination of tolerable risk (see Annex K); (c) a number of different methods that enable the safety integrity level (SIL) for the safety instrumented functions (SIF) to be determined (see Annexes B through K); and (d) the impact of multiple safety systems on calculations determining the ability to achieve the desired risk reduction (see Annex J).