What is a COMAH (Control of Major Accident Hazards) Site?
9 March 2025
A COMAH site refers to a facility that falls under the Control of Major Accident Hazards Regulations (COMAH). These regulations are designed to prevent and mitigate the effects of major industrial accidents involving dangerous substances. The UK’s Health and Safety Executive (HSE), along with the Environment Agency (EA) in England, Natural Resources Wales (NRW), and the Scottish Environment Protection Agency (SEPA), enforces these regulations to protect people and the environment.
Purpose of COMAH Regulations
The primary aim of COMAH is to:
- Prevent major accidents involving hazardous substances.
- Limit the impact of such accidents on people, property, and the environment.
The regulations apply to industries handling significant quantities of dangerous substances, such as chemicals, fuels, and explosives. These substances, if not managed properly, could lead to catastrophic incidents like fires, explosions, or toxic releases.
What Qualifies as a COMAH Site?
A COMAH site is any location where dangerous substances are present in quantities above certain threshold levels specified in the COMAH Regulations 2015. These sites are classified into two tiers based on the amount of hazardous materials stored or used:
Lower-tier COMAH sites – Sites that hold dangerous substances above the lower threshold but below the upper threshold. They must demonstrate proper safety management and risk control measures.
Upper-tier COMAH sites – Sites that exceed the upper threshold and are subject to stricter regulations, including producing a Safety Report to demonstrate how major accident risks are managed.
Industries Affected by COMAH
COMAH regulations apply to a range of industries, including:
- Chemical manufacturing plants
- Oil refineries and fuel storage facilities
- Pharmaceutical production sites
- Explosives manufacturers and storage facilities
- Some food and drink production sites (e.g., those handling large quantities of alcohol or ammonia)
- Waste treatment and recycling plants
Responsibilities of COMAH Site Operators
Operators of COMAH sites must:
- Identify and assess hazards – Conduct risk assessments to understand potential accident scenarios.
- Implement risk control measures – Put in place procedures and safety management systems to prevent accidents.
- Prepare emergency plans – Develop internal and external response plans in collaboration with local authorities and emergency services.
- Notify regulatory authorities – Inform the HSE and environmental agencies if their site meets COMAH thresholds.
- Report incidents – If a major accident occurs, operators must report it to the relevant authorities and take corrective action.
Local Authority and Public Involvement
For upper-tier COMAH sites, local authorities play a key role in off-site emergency planning. This includes:
- Informing the public about risks and safety measures.
- Conducting joint exercises with emergency services.
- Ensuring preparedness for major accidents.
The public has a right to access information about COMAH sites in their area, including details of hazardous substances and emergency response measures.
COMAH sites are regulated to ensure the safe handling of hazardous substances, reducing the likelihood of major industrial accidents. The stringent controls and emergency planning requirements help protect workers, local communities, and the environment. Businesses operating within these regulations must take their responsibilities seriously to ensure compliance and safety at all times.
For more information, visit the HSE website or consult your local environmental agency.
