Control of Major Accident Hazards Regulations (COMAH) 1999

Posted on: 19 April 2013

These regulations came into force on 1 April 1999 and were subsequently amended 30 June 2005.

The aim of COMAH is to prevent major accidents involving dangerous substances and limit the consequences to people and the environment of any accidents which do occur.

It has been recognised for many years that certain industrial activities involving dangerous substances have the potential to cause accidents that may give rise to serious injury to people, or damage to the environment. Such activities have come to be known as major accident hazards.

The regulations operate at two levels (top tier and lower tier) depending on the quantities of dangerous substances at an establishment.

Dangerous substances include those that are toxic; oxidizing; explosive; flammable or otherwise dangerous to the environment.

Regulation 4 (general duty) states that “every operator shall take all measures necessary to prevent major accidents and limit their consequences to persons and the environment”.

This duty underpins the whole of the regulations and requires operators to perform a risk assessment of all identified hazards and develop measures that prevent and mitigate the consequence of any potential major accident.

Relationship with the Pressure Systems Safety Regulations (PSSR) 2000

The purpose of this technical bulletin is to highlight the general requirement of COMAH and to provide an awareness to the operator and the Engineer Surveyor of the relationship between COMAH and PSSR.

The aim of PSSR is to prevent serious injury from the hazard of stored energy as a result of the failure of a pressure system. With the exception of the scalding effects of steam, these regulations do not consider the hazardous properties of the contents released following any system failure.

It is inevitable that an establishment that falls under the requirements of COMAH may also contain a pressure system. It is important therefore, because of the different aims of these two regulations, to recognise that an examination that satisfies the requirements of PSSR may not satisfy the requirements of COMAH without additional examinations being carried out i.e. Non Destructive Testing (NDT).

The operator must consider all these aspects when deciding on the level of precautions required to ensure that their obligations under Regulation 4 of COMAH are met.

For more information on this subject contact our Engineering Standards department on 01483 265799.