Control of major accident hazards (COMAH)

COMAH regulated site responsibilities


If you operate a site covered by the Control of Major Accident Hazard (COMAH) Regulations, you must meet requirements for using and storing dangerous substances.

Notify the Competent Authority (CA)

If the COMAH Regulations apply to your site, you must notify the CA before you use or store dangerous substances. You must also tell the CA before starting any new operation and send them any additional information they need.

The notification must give details about the operator, the site, the processes carried out and an inventory of the dangerous substances present. 

If there are any significant changes to the information you provided in your notification you must tell the CA immediately. You must also tell them if your site closes, or if any part of the site closes where dangerous substances are handled, produced, used or stored.

Assess the risks and prepare a major accident prevention policy

You must take all necessary measures to prevent major accidents and have plans, systems and procedures in place at your site. You must be able to demonstrate this to the Competent Authority (the HSENI and the Northern Ireland Environment Agency (NIEA)).

You must carry out assessments to understand and predict how a major accident could happen on your site and the possible consequences of a major accident. Situations to consider include:

  • leaks and spills due to vessel or pipework failures
  • explosions, eg caused by mixing incompatible chemicals in reactors
  • fires, eg in processing areas, warehouses or chemical or fuel storage areas

You must prepare a major accident prevention policy (MAPP) document. This should outline your approach to the control of major accident hazards on your site.

You must also prepare a safety management system document. This should cover the detailed steps you will take to control major hazards. It should also show the structure of your organisation and the responsibilities, procedures and resources for putting the MAPP into action.

For further details, you should contact the HSENI or the NIEA, or check schedule 2 of the COMAH Regulations

Comply with the COMAH containment policy

You must comply with the COMAH containment policy if you store liquid dangerous substances in bulk. You must:

  • ensure your primary containment, eg storage tanks, are designed and constructed to relevant standards
  • use suitable secondary containment, eg a bund, to contain any liquid which escapes from a primary container or its equipment
  • develop plans to help reduce the off-site impacts of an incident

Deal with incidents correctly

If a major accident occurs, such as a significant leak, spill, fire or explosion, you must take all necessary steps to minimise its effects on people and the environment.

You should implement your emergency procedures. These will be part of your MAPP or, for top tier sites, must be a separate plan.

You should contact the HSENI immediately by calling the 24-hour HSENI Helpline on Tel 0800 032 0121.

You should also report the incident to the HSENI.

You should also report any pollution incident as soon as it happens to the NIEA Water Pollution Hotline on Tel 0800 80 70 60.

Make sure that your staff are aware of these phone numbers and know what to do if an incident happens.

  • HSENI Helpline
    0800 032 0121