This Guide, written by leading experts, including from the Health & Safety Executive, provides guidance and recommendations on the application of IEC 61511 for the specification and implementation of safety instrumented systems, systems designed to bring a process plant to a safe state should a hazardous incident occur. EEMUA 222 is intended to explain how to use the IEC 61511 standard effectively and addresses the responsibility and deliverables of organisations involved in the specification, supply and maintenance of safety instrumented systems. IEC 61511, 'Functional safety - Safety instrumented systems for the process industry sector' is now widely accepted as the state of the art for such systems. The Guide is supplied with a CD (purchasers will need to request the access password to read the CD).