A "worst case" methodology for obtaining a rough but rapid indication of the societal risk from a major accident hazard installation.

This paper describes a methodology developed to provide a rough but rapid indication of the magnitude of the societal risks at and in the vicinity of a major accident hazard installation. It is intended to be used by the UK Health & Safety Executive (HSE) as a first screening tool when examining safety reports submitted under The Control of Major Accident Hazards (COMAH) Regulations 1999. These are the Regulations which implement in the UK the major aspects of Council Directive 96/82/EC, the "Seveso II" Directive. Within the methodology a new weighted risk integral parameter is defined, suitable for comparison with criteria, and its value calculated. The paper includes examples to illustrate the use of the methodology.