Gives requirements for the specification, design, installation, operation and maintenance of a safety instrumented system, so that it can be confidently entrusted to place and/or maintain the process in a safe state. This standard has been developed as a process sector implementation of IEC 61508. Experts in IEC Subcommittee 65A (System aspects) explain that this sector specific standard of IEC 61508 addresses the functional safety of safety instrumented systems (SIS) for the process sector. The purpose is to ensure that the safety integrity of safety instrumented systems is adequate taking into account the associated hazards &risks. It falls under the generic IEC 61508 standard and thus required adjustment to the requirements found in IEC 61508 (generic in content since it covers all sectors) to cover process sector needs. The standard will mainly be used by integrators and operators of chemical, petro-chemical and gas process plants. It also has applications in non-nuclear power generation. It will also be used as a benchmark by those responsible for assessing the adequacy of such plants including certification bodies and regulators. IEC 61511-2 Ed. 1.0: Functional safety instrumented systems for the process industry - Part 2: Guidelines in the application of Part 1 is scheduled to appear in June 2003. IEC 61511-3 Ed. 1.0: Functional safety: Safety instrumented systems for the process industry sector - Part 3: Guidance for the determination of safety integrity levels wil be published shortly.