Control of Major Accident Hazards Regulations


The Control of Major Accident Hazards (COMAH) Regulations ensure that businesses take all necessary measures to prevent major accidents involving dangerous substances and limit the consequences to people and the environment of any major accidents which occur.

The Seveso Directive

The Seveso Directive was introduced following a disaster in the Italian town of Seveso in 1976. It aims to prevent major accidents involving dangerous substances and to limit consequences of such accidents for people and the environment. It was subsequently broadened as Seveso II.

In Northern Ireland the directive is implemented through the Control of Major Accident Hazards Regulations (COMAH), by a joint Competent Authority(CA), made up of the Health and Safety Executive for Northern Ireland and the Northern Ireland Environment Agency.

COMAH applies when a site has more than a threshold quantity of dangerous substances present (Lower Tier). Sites are subject to more stringent controls if the quantities of substances present are above a higher threshold (Top Tier).


Site safety management

Lower tier sites are required to prepare a Major Accident Prevention Policy. Top tier sites prepare the more detailed Safety Report. Regular inspections and ongoing advice are provided by the Competent Authority. Learnings from relevant incidents are incorporated for example from Buncefield.


Emergency planning

Development of off-site emergency plans are arranged by the competent authority. Emergency plans are tested by the emergency services, with the involvement of the COMAH site and the competent authority.


Land use planning

New development in the vicinity of COMAH sites is considered as part of planning approval processes. HSENI advise planning services by applying the PADHI guidelines (Planning Advice for Developments near Hazardous Installations). 



Key legislation

Please note that these links are to the original legislation, visitors should verify for themselves whether legislation is in force or whether it has been amended or repealed by subsequent legislation.