A Safety Instrumented Function (SIF) is a set of equipment intended to reduce the risk due to a specific hazard that is designed to prevent or mitigate a hazardous event. The SIF has an assigned SIL (Safety Integrity Level), and one or more SIFs comprise a SIS (Safety Instrumented System).

Reference Definition by Aiche.org: Safety Instrumented Functions (SIF) is a system composed of servers, logic servers, and final control elements for the purpose of taking the process to a safe state when predetermined conditions are violated.

Related Definitions in the Project: The Process Safety Engineering; Engineering; CSI Engineering