UK: Control of Major Accidents Hazards Regulations 1999 (COMAH)

Last Updated: 25 June 1999

In 1976, an accident occurred at a chemical plant in Seveso, Italy. A process involving pesticides went out of control causing a toxic release which led to extensive contamination in the surrounding area. Borne out of this incident was the first Seveso Directive which was implemented in this Country as The Control of Industrial Major Accident Hazards Regulations 1984 (CIMAH).

In February 1997, the European Commission passed the second Seveso Directive which on the 1st April 1999 came into force as COMAH. These new regulations effectively build upon the core obligations under CIMAH but now extend the scope of those regulations to include the environment, thus bringing about a unique calibration between the HSE and the Environment Agency.

The purpose of COMAH is to prevent and limit the effects of major accidents from sites which have the potential to cause harm both to the public and to the environment.

Whilst the two tier system which existed under CIMAH has been retained, the criteria for qualification under the regulations has changed.

CIMAH listed 170 named chemicals and drew a distinction between process and storage. The CIMAH regulations are triggered by the presence of specified quantities of dangerous substances. However, less reliance is placed upon named substances (there are only 38 listed in COMAH) and relies largely upon the use of generic categories such as "toxic", "flammable" and "dangerous for the environment". There are 10 categories altogether which are based upon the CHIP Regulations 1994.

Enforcement of the regulations is undertaken by the "Competent Authority".

In a departure from the Directive, the regulations enable the Competent Authority to charge operators. The scheme is to be administered by the HSE and charges will be calculated as "actuals" ie reflecting the actual costs incurred by the officers concerned. Charging guides have already been issued to all operators indicating that the hourly rates for 1999/2000 are £102 for both the HSE and the Environment Agency. In Scotland where the Competent Authority consists of the HSE and the Scottish Environmental Protection Agency, the rates are reduced to £86 for the Agency.

If you are covered by COMAH, the nature of the duties imposed upon you will differ according to whether you are classed as a "lower tier" or "top tier" site.

Lower Tier sites

Paragraph 3 of the Regulations includes the following basic details which you must lodge with the competent authority:-

  • Name and address of operator.
  • Address of establishment.
  • Name and position of person in charge.
  • Details of dangerous substances on site.
  • Site activity.
  • Environmental details.

If you have already filed this information under CIMAH, you do not have to do so again.

Lower tier sites must also take all measures necessary to prevent major accidents and to limit their consequences to people and the environment. This is the general duty at the core of the Regulations and applies to all COMAH operators.

The duty recognises that the measures taken must be proportionate to the risk which exists. Prevention must be based on the principle of reducing risk to a level as low as is reasonably practicable (ALARP) and using the best available technology not entailing excessive cost (BATNEEC) for environmental hazards.

Additionally, lower tier sites must also prepare a major accident prevention policy (MAPP).

This will set out what is to be achieved in simple terms and will refer to the safety management system which will put the policy into action. The detail will be found in other documentation such as plant operating procedures, training records, job descriptions and audit reports.

The MAPP must also address those aspects of the safety management system listed in Schedule 2 of the Regulations. Essentially these are:-

  • Organisation and Personnel.
  • Identification and evaluation of major hazards.
  • Operational control.
  • Planning for emergencies.
  • Monitoring audit and review.

Top Tier sites

Operators of top tier sites have the same duties as lower tier operators except that there is no need to prepare a separate MAPP as the information required by the MAPP is provided in the form of a safety report.

The purpose of the safety report is to demonstrate that "all measures necessary for the prevention and mitigation of major accident have been taken". The report must include:-

  • A policy on how to prevent and mitigate major accidents.
  • A management system for implementing that policy.
  • An effective method for identifying any major accidents that might occur.
  • Measures (such as safe plant and safe operating procedures) to prevent and mitigate major accidents.
  • Information on the safety precautions built into the plant and equipment when it was designed and constructed.
  • Details of measures (eg firefighting, relief systems and filters) to limit the consequences of any major accident that might occur.
  • Information about the emergency plan for the site. This is also used by the Local Authority in drawing up an offsite emergency plan.

These reports will be made public via registers subject to national security, commercial and personal confidentiality considerations. The safety report must be updated every 5 years or after any significant changes or new knowledge about safety matters.

Top tier operators are also required to prepare and test an on site emergency plan and supply information to Local Authorities for off site emergency planning purposes. This must be undertaken by no later than the deadline for completion of the on site emergency plan and will require operators to meet with their Local Authorities in order to determine their exact needs.

Finally, certain information must be provided to the public by operators of top tier sites. Schedule 6 of the Regulations sets out the information which must be given to people who may be affected by an accident at a COMAH establishment:-

  • The dangerous substances.
  • The possible major accidents.
  • Their consequences.
  • What to do in the event of an accident.

This information must be provided within a reasonable time after the offsite emergency plan has been prepared. The HSE consider a period of 6 months to be reasonable.

As a lower tier operator, you may expect a minimum of one inspection every 3 years. Top tier operators will be inspected a minimum of once per year with a more detailed audit being undertaken at least once during the 5 year safety report cycle.

Whilst the UK was some 2 months late in enacting the Directive the Chemical Industries Association (CIA) has criticised the fact that when the Regulations came into force, not all the guidance promised by the HSE was available.

The change in criteria for establishments coming within the Regulations will result in premises which would not have fallen within CIMAH suddenly being declared CIMAH sites. The CIA has alerted its members to the fact that they will need to be sensitive to the concerns of local residents and, if necessary, to undertake public relations exercises to explain why the site is now designated as subject to major accident hazard controls.

The operation of COMAH relies to some extent on the co-ordination of the regulators as to inspections and the exchange of information. Whilst a Memorandum of Understanding has been reached between the HSE and the Environment Agency it remains to be seen how that will work in practice. As the HSE have justified the existence of a charging scheme on the basis that it will provide less of a burden to the tax payer, it is hoped that co-operation between the regulators will prevent those charges representing an unreasonable burden to industry.


For further information please contact Mike Shepherd, Trinity Court, 16 John Dalton Street, Manchester, M60 8HS, UK, Tel: +44 161 830 5000

This article was first published in the May 1999 issue of Hammond Suddards' Safety, Health and Environment News Newsletter.

The information and opinions contained in this article are provided by Hammond Suddards. They should not be applied to any particular set of facts without appropriate legal or other professional advice.

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