Understanding COMAH And How It Works


COMAH means – Control of Major Accident Hazards.

Control of Major Accident Hazards regulation (COMAH Regulation) is a 2015 regulation which:

  • Take all necessary measures to prevent major accidents involving dangerous substances, and also
  • Limit the consequences to people and the environment of any major accidents which do occur.

The overall objective is to provide a high level of protection in a consistent and effective manner.

NOTE: The Control of Major Accident Hazards 2015 regulation launched on the 1st of June 2015 was a replacement for the  CoMAH 1999.


Read AlsoWhat is Hazmat Test

Who Enforces COMAH

Control of Major Accident Hazards regulation 2015 is enforced in Great Britain by the COMAH competent authority (CA). This comprises five public bodies working in partnership;

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

This Regulations implement the Seveso III Directive (2012/18/EU).


Where does this regulation apply

It 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). Lower tier sites are required to prepare a Major Accident Prevention Policy while top tier sites prepare the more detailed Safety Report.


Read AlsoWhat is COSHH – What is the full meaning of COSHH


This regulation was a response to a serious industrial accident which occurred on 10th July 1976 in the town of Seveso in the Lombardy region of Italy where 1kg of 2, 3, 7, 8-tetrachlorodi-benzo-p-dioxin (TCDD) into the environment. This accident resulted to:

  • Dead of over 3,000 animals
  • 80,000 more slaughtered to prevent the dioxin entering the food chain.
  • Approximately 500 cases of the skin disease chloracne reported.
  • Financial cost rose to about $150 million.

The result of this accident led to the Seveso III Directive which led to the “Control of Major Accident Hazards Regulations”.

Read AlsoRIDDOR (Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995)


COMAH Training

The course covers all aspects of the COMAH Regulations, including information on creating a Major Accident Prevention Policy (MAPP), and provides learners with an understanding of their responsibilities under the latest Seveso III Directive which applies to all COMAH establishments from 1st June 2015.