This Guide provides guidance and recommendations on IEC 61511-1 and, asappropriate, IEC 61508 for the specification and implementation of safetyinstrumented systems (SIS) in the UK process industries.It provides guidance only where it is considered necessary or useful. Therelevant sub-clauses of IEC 61511-1 are referenced in a right-hand column.Clauses marked ** give recommendations beyond the scope of IEC 61511-1where they are worthy of consideration. Such recommendations are consideredto be good practice in the UK. This Guide does not take precedence over, repeator replace any requirement of IEC 61511-1 or IEC 61508.This Guide is applicable to process industries such as onshore and offshore oil andgas, non-nuclear power generation, chemicals and petrochemicals. Other processindustries may choose to use the guidelines at their own discretion.It outlines general information for all users, plus guidance on organisationalresponsibilities for end users, designers, suppliers (of systems and products),integrators, installers and maintainers. It does not provide checklists or detail onhow to design, operate and maintain such systems.This Guide is for use in applications relating to safety of people, but its principlesmay also be applied to environmental and asset/commercial protection.