Control of Major Accident Hazards (COMAH)


In the UK, the Control of Major Accident Hazards Regulations 1999 set out what businesses need to comply with. Having come into force on 1 April 1999 they are amended by the Control of Major Accident Hazards (Amendment) Regulations 2005. These implement the Seveso II Directive (96/82/EC as amended by Directive 2003/105/EC), replacing the Control of Industrial Major Accident Hazards Regulations 1984.

COMAH applies mainly to the chemical industry, but also to some storage activities, explosives and nuclear sites, and other industries where threshold quantities of dangerous substances identified in the Regulations are kept or used. The main aim is to prevent and mitigate the effects, on people or the environment, from major accidents involving dangerous substances. The COMAH Regulations treat risks to the environment as seriously as those to people.

Land-use planning requirements of the Directives are implemented by separate land-use planning legislation that is the responsibility of the Office of the Deputy Prime Minister, the Scottish Executive, and the National Assembly for Wales.

The regulations are enforced through a joint Competent Authority in the UK.

The Competent Authority (CA)

The Competent Authority comprises five organisations:

  • Health Safety Executive (HSE);
  • Office for Nuclear Regulation (ONR);
  • Natural Resources Wales (NRW);
  • Environment Agency (EA) (for England); and,
  • Scottish Environmental Protection Agency (SEPA)

These five organisations are responsible for the enforcement of the Control of Major Accident Hazard (COMAH) Regulations.

The Competent Authority Strategic Management Group (CASMG) is responsible for setting a strategic direction and plan of work for the CA as a whole. Importantly CASMG is responsible for reporting back publicly on progress both in the UK and to the European Union. CASMG comprises senior representatives from each of the regulatory authorities enforcing COMAH in the UK.

Changes due in 2015

The Seveso II Directive is the main piece of EU legislation that deals specifically with the control of on-shore major accident hazards involving dangerous substances. The Seveso II Directive will be replaced by the Seveso III Directive on 1 June 2015. In order to implement the new Directive, the COMAH Regulations 1999 will be repealed and replaced by the COMAH Regulations 2015 on 1 June 2015.

The main changes include a change in the chemical classification system from CHiP to Classification, Labelling and Packaging of Substances and Mixtures Regulations (CLP Regulations). There are other changes that increase the public access to information and place a duty on the Local Authorities to produce, review and test external emergency plans at upper tier establishments.

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