COMAH 2015: HSE Major Accident Hazards Rules

Regulatory citation: Control of Major Accident Hazards Regulations 2015 (SI 2015/483)

What Are the COMAH Regulations?

The Control of Major Accident Hazards Regulations 2015 (COMAH) apply to establishments in Great Britain where dangerous substances are present at or above the thresholds in Schedule 1. They aim to prevent major accidents, such as large releases, fires or explosions, and to limit their consequences for people and the environment. COMAH applies mainly to the chemical industry, but also covers fuel storage, gas sites and other operations holding large inventories.

Sites are either lower tier or upper tier. Lower tier sites hold dangerous substances at or above the Schedule 1 column 2 quantity. Upper tier sites hold them at or above the column 3 quantity and have extra duties.

Why COMAH Matters

A single major accident can kill workers and neighbours, pollute rivers and close a business. COMAH requires operators to show, in writing, that they understand their hazards and have the controls and emergency plans to deal with them.

Core Obligations

1. Check Whether Your Site Is In Scope (reg 2 and Sch 1)

Compare your actual and anticipated inventory with the named substances in Schedule 1 Part 2 and the hazard categories in Part 1. For example, the lower and upper tier quantities are 10 and 25 tonnes for chlorine, 5 and 50 tonnes for hydrogen, 50 and 200 tonnes for LPG and natural gas, and 2,500 and 25,000 tonnes for petroleum products such as gasolines, kerosenes and gas oils. Where no single substance qualifies, the aggregation rule in Schedule 1 Part 3, note 4, adds substances together by hazard group.

2. Take All Measures Necessary (reg 5)

Every operator must take all measures necessary to prevent major accidents and limit their consequences to human health and the environment. Operators must be able to demonstrate this to the competent authority, which is HSE (or the Office for Nuclear Regulation on nuclear sites) acting jointly with the appropriate environment agency.

3. Notify the Competent Authority (reg 6)

New establishments must notify within a reasonable period before construction and before operation starts. Notifications cover the operator, the site, the dangerous substances and quantities, the activities and the surroundings. Operators must notify in advance of significant changes to inventory, substances or processes, and of permanent closure.

4. Prepare a Major Accident Prevention Policy (reg 7)

All operators must prepare and keep a written major accident prevention policy (MAPP) and put it into effect through a safety management system meeting Schedule 2. The MAPP must be reviewed after significant changes and at least every five years.

5. Upper Tier: Submit and Review a Safety Report (regs 9 and 10)

Upper tier operators must send a safety report to the competent authority within a reasonable period before construction or operation starts. They must not start until the authority has communicated its conclusions. The report must be reviewed at least every five years and after a major accident, new knowledge or significant change.

6. Upper Tier: Prepare and Test an Internal Emergency Plan (reg 12)

Upper tier operators must prepare an internal emergency plan after consulting the people working at the establishment, the emergency services, the environment agency, health bodies and the local authority. The plan must be reviewed and tested at intervals of no more than three years. The local authority prepares an external emergency plan.

7. Inform the Public (regs 17 and 18)

Operators must give the competent authority information for publication about their site and hazards. Upper tier operators must also actively give safety information to everyone in the area the competent authority sets, including schools and hospitals. This must be reviewed at least every three years and sent again at least every five years.

8. Act After a Major Accident (reg 26)

After a major accident, the operator must inform the competent authority as soon as practicable, with details of the circumstances, substances, effects and emergency measures, and the steps planned to prevent a recurrence.

Common Compliance Approaches

Keep a Live Inventory

Track dangerous substance quantities by hazard category so changes that could alter your tier are spotted early.

Link the MAPP to Daily Work

Turn the MAPP into practical safety management system procedures, such as permits, management of change and audits.

Exercise Emergency Plans

Run joint exercises with the fire and rescue service and the local authority so roles are clear before an incident.

Example: COMAH in Practice

A fuel distribution company plans to expand its terminal, which would take its petroleum products storage above 25,000 tonnes. It notifies the competent authority, updates its MAPP and prepares an upper tier safety report before construction starts. It consults workers and emergency services on a new internal emergency plan, schedules a test within three years, and works with the local authority to send safety information to nearby homes and a primary school.

Related regulations: DSEAR explosive atmospheres, OSHA process safety management, EPA risk management program.

Note: This summary reflects COMAH as it applies in Great Britain. Northern Ireland has equivalent but separate legislation. Always check the current legislation and HSE and environment agency guidance.

Frequently Asked Questions

What is the difference between lower tier and upper tier COMAH sites?

Lower tier sites hold dangerous substances at or above the Schedule 1 column 2 quantities. Upper tier sites hold them at or above the column 3 quantities and must also prepare a safety report, an internal emergency plan and public information.

How often must a COMAH safety report be reviewed?

At least every five years, and also after a major accident, new safety knowledge, or changes that could significantly affect major accident hazards.

Who is the COMAH competent authority?

HSE acting jointly with the appropriate environment agency, or the Office for Nuclear Regulation acting jointly with that agency for nuclear sites.