 Via a Layer of Protection Analysis (LOPA) or some other approved method, Integrity Levels (IL) are defined for the SIFs in their respective scenarios.The Integrity Levels may be categorised as Safety Integrity Level (SIL) or Environmental Integrity Level (EIL).Based on HAZOP study recommendations and the IL rating of the SIFs; the engineering (including the BPCS and the SIF designs) for each unit operation is finalized.