CoMAH 2015: What you need to know about the new regulations

toxic_wasteOn 1 June 2015 the Control of Major Accident Hazards Regulations 2015 (CoMAH) replaced CoMAH 1999, which has now been revoked. The purpose of the CoMAH regulations is to prevent major accidents involving dangerous substances – such as a major emission, fire, or explosion – and limit the consequences to people and the environment of any accidents which do occur. In this short post*, we explore the background to CoMAH, as well as highlighting the key changes you need to be aware of.

Background to CoMAH

Like many safety regulations, CoMAH was a response to a serious industrial accident. At around 12.30pm on 10 July 1976, a runaway reaction occurred in a small chemical plant close to the town of Seveso in the Lombardy region of Italy. This led to the release of approximately 1kg of 2, 3, 7, 8-tetrachlorodi-benzo-p-dioxin (TCDD) into the environment. It was by far the highest environmental dioxin release to date, contaminating approximately six square miles of soil surrounding the chemical plant. The release killed over 3,000 animals (mostly poultry and rabbits). A further 80,000 were slaughtered to prevent the dioxin entering the food chain. No human deaths were attributed to the dioxin release, although many people fell ill (approximately 500 cases of the skin disease chloracne were reported). The financial cost, which included a huge clean-up operation, eventually rose to about $150 million. iStock_000016322937Small

The Seveso disaster resulted in a new European Directive on the major accident hazards of certain industrial activities. Adopted in June 1982, Council Directive 82/501/EEC became more commonly known as the Seveso Directive after the town most affected by the disaster.

The directive, which was later amended in view of the lessons learned from accidents such as Bhopal, specifically covers those sites manufacturing, using or handling large quantities of hazardous substances. Currently, Seveso applies to more than 10,000 industrial establishments in the EU.

CoMAH 2015

The overall aim of CoMAH is to ensure that necessary measures are taken to prevent and limit the effects of major accidents involving dangerous substances. Under the regulations establishments fall into three main groups:

  • Upper tier establishments: associated with the highest potential risks (these were referred to as top tier sites in CoMAH 1999)
  • Lower tier establishments: associated with lower risk but are still within the scope of CoMAH
  • Sites which do not fall within the scope of CoMAH

The hazards and amounts of substances on-site determine whether that site falls into the scope of CoMAH and, if so, to which tier that site belongs. Qualifying quantities based on classification are given in Schedule 1, Part 1 of the regulations. Some substances are designated as named substances which have different qualifying quantities from those of the generic classification. For each of these substances the qualifying amount is specified in Schedule 1, Part 2 (Part 2 overrides Part 1).

The main features/requirements of the regulations include:

  • Notification: where quantities of dangerous substances on a site meet or exceed thresholds laid down by CoMAH, the operator must notify the relevant Competent Authority (CA).
  • MAPP: All CoMAH establishments must prepare a Major Accident Prevention Policy. This does not have to go into detail, but is rather a general statement about how the site will prevent major accidents.
  • SMS: all establishments must have a Safety Management System to implement the MAPP.
  • CoMAH Safety Report: (upper tier establishments only). This is a detailed report of the arrangements in place to prevent and limit the effects of major accidents.
  • On-site emergency plan (upper tier establishments only). Sites must prepare, review and test an on-site emergency plan to control, contain and mitigate the effects of a major accident.
  • Provision of information to be made available to
    • Local authorities for off-site emergency planning purposes (upper tier establishments only).
    • The public, particularly those likely to be most affected by a major accident.
    • A neighbouring member state which may be affected by a major accident.
    • Other nearby sites which may themselves have inventories of hazardous substances.

In Great Britain, CoMAH is enforced by the CoMAH Competent Authority (CA), which consists of the Health and Safety Executive (or in the case of nuclear sites, the Office for Nuclear Regulation) together with the relevant regional environment agency. The CA’s role is “to oversee and coordinate the regulation of major hazards in the UK and ensure that the regime operates effectively”.

Main changes to CoMAH

According to the HSE:

‘Change has been kept to a minimum as far as possible in producing the COMAH Regulations 2015 to implement the Seveso III Directive. However, there are changes that operators and other stakeholders will need to familiarise themselves with.

The Seveso III Directive, and by extension the COMAH Regulations 2015, apply to any business where dangerous substances, as set out in Annex 1 of the Directive, are either present on site at or above the threshold quantities or could be generated in the event of an accident. All types of businesses with dangerous substances are covered, not just those in the chemical sector.’

The changes from Seveso II to III have been summarised here.


The changes described in this article may be painful in the short term. However, the potential benefits of this move towards globalisation include a more uniform approach to health and safety and the economic largess of a level playing field. coshh Skull Quiz

Given the complexity of this task, one option for sites may be to get expert help. Guidance is also available from HSE, which has produced a comprehensive guidance document to the regulations, that can be downloaded for free from the HSE website.


*This post is an abridged version of an article written by Nick Cook that originally appeared in RoSPA’s Occupational Safety & Health Journal.

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