Control Of Major Accident Hazards Regulations 2015 (COMAH)

Background for operators

COMAH15 implements the Seveso III Directive, except for the land-use planning requirements, which are implemented by changes to planning legislation. COMAH15 replaced the Control of Major Accident Hazards Regulations 1999 (COMAH99) and came into force on 1 June 2015. This page outlines the main duties under the regulations and explains what you need to do if they apply to you. Key duties for lower and upper tier operators are detailed in the HSE publication L111 Control of Major Accident Hazards Regulations (COMAH) 2015.

Further information and guidance is available on the COMAH pages of the HSE website, including the following CA guidance documents:

Information is also available on the websites of the Scottish Environment Protection Agency and Natural Resources Wales websites.

The main aim of COMAH

COMAH aims to prevent and mitigate the effects of major accidents involving dangerous substances which can cause serious damage/harm to people and/or the environment. COMAH treats risks to the environment as seriously as those to people.

Changes introduced by the COMAH15 regulations

Although many duties will be familiar from COMAH99, COMAH15 introduced some changes including:

  • the list of dangerous substances now in scope has been updated and aligned to the CLP Regulations
  • some definitions have changed
  • for emergency planning, there is a new requirement for cooperation by designated authorities (Category 1 responders, as defined in the Civil Contingencies Act 2004) in tests of the external emergency plan
  • there are new requirements for public information, including  provision of basic information on all establishments - a public information database has been developed to support this
  • broadening of the 'domino effects' duty for members of a domino group to cooperate and share relevant information with neighbouring establishments and non-COMAH sites

The COMAH competent authority

A key feature of the COMAH Regulations is that they are enforced by a competent authority. The competent authority for an establishment is HSE or the Office for Nuclear Regulation (ONR) for nuclear establishments, together with the appropriate agency. In England the competent authority is HSE or ONR and the Environment Agency (EA); in Scotland it is HSE or ONR and the Scottish Environment Protection Agency (SEPA); and in Wales it is HSE or ONR and Natural Resources Body for Wales (NRW).

The regulations place duties on the CA to inspect activities subject to COMAH and prohibit the operation of an establishment if there is evidence that measures taken for prevention and mitigation of major accidents are seriously deficient. It also has to examine safety reports from upper tier establishments and inform operators about the conclusions of its examinations in a reasonable time period.

Cost recovery

The CA recovers costs for the work it does on COMAH on an actuals basis ie recovery of the full costs of the time spent by the CA in carrying out COMAH-related activities for a particular establishment.

The COMAH Charging Review Group (CCRG) has industry representation and meets annually to discuss the operation of the financial and administrative arrangements of the cost recovery regime.

For further information see:

Cost recovery for COMAH activities: A guide

Industries and activities that might be in scope

COMAH mainly affects the chemical industry, but also some storage activities, explosives sites, nuclear sites and other industries, where threshold (and above) quantities of dangerous substances identified in the regulations are kept or used.

Schedule 1 of the regulations lists the dangerous substances or the categories of dangerous substances which cause the duties to apply and the quantities which set the two thresholds for application – at 'lower tier' and 'upper tier'.

Operators of sites holding larger quantities of dangerous substances and notifying as upper tier sites are subject to more requirements than lower tier sites.

What you need to do

Firstly you need to determine if the regulations apply to you. Regulation 3, together with Schedule 1, will provide the answer. If the amounts of dangerous substances present on site take you over the lower threshold then the lower tier duties apply. If the amounts of dangerous substances exceed the higher threshold then the upper tier duties apply. Appendix 1 of COMAH15 will assist you in determining whether you are lower or upper tier.

General operator duties

Notify basic details to the CA

Operators of all establishments subject to COMAH must notify certain basic details to the CA using the COMAH notification form, which must be sent to the appropriate HSE e-mail address. The key points which have to be included in the notification are given below but full details are given in Regulation 6:

  • the name and address of the operator
  • the address of the establishment
  • the name or position of the person in charge
  • details of dangerous substances on-site (a breakdown is required for petroleum products)
  • site activities
  • environmental details

Full details of how to notify are available on the HSE website's COMAH Notifications pages.

Take all measures necessary to prevent major accidents and limit their consequences to people and the environment

This is the general duty on all operators. It is a high standard and applies to all establishments in scope. By requiring measures both for prevention and mitigation there is a recognition that all risks cannot be completely eliminated. This in turn implies that proportionality must remain a key element in the enforcement policy of HSE and the agencies. The phrase 'all measures necessary' will be interpreted to include this principle and inform the CA's judgment about the measures in place.

Where hazards are high, high standards will be required to ensure risks are acceptably low, in line with the CA's policy that enforcement should be proportionate. Prevention should be based on the principle of reducing risk to a level as low as is reasonably practicable (ALARP) for human risks and using the best available technology (BAT) for environmental risks. The ideal should always be, wherever possible, to avoid a hazard altogether.

Duties for lower tier operators

Prepare a major accident prevention policy

Regulation 7 requires that every operator must prepare and retain a major accident prevention policy (MAPP).

The MAPP will usually be a short, simple document setting out what is to be achieved. But it should also include a summary and further references to the safety management system that will be used to put the policy into action. The detail will be contained in other documentation relating to the establishment, for example plant operating procedures, training records, job descriptions and audit reports, which the MAPP can refer to.

The MAPP also has to address issues relating to the operator's safety management system. The details are given in Schedule 2 but the key areas are:

  • organisation and personnel
  • identification and evaluation of major hazards
  • operational control
  • management of change
  • planning for emergencies
  • monitoring, audit and review

Duties for upper tier operators

Upper tier operators are required to have a MAPP, which must be included as a separate document in the safety report, and also have the following additional duties.

Prepare a safety report

All operators of upper-tier establishments are required to prepare a safety report. Its purpose is to show that you have put in place arrangements for the control of major accident hazards and to limit the consequences to people and the environment of any that do occur. The purposes and minimum content of a safety report are set out in Regulations 8 and 9 and Schedule 3 to the regulations.

The safety report must include:

  • a description of the establishment and its environment including the geographical location, meteorological, geological, hydrographic conditions and, if necessary, its history
  • a description of processes, in particular the operating methods, where applicable, taking into account available information on best practices
  • a description of dangerous substances, including their classification under the CLP Regulation and  an inventory of dangerous substances
  • a detailed description of the possible major accident scenarios and their probability or the conditions under which they might occur including a summary of the events which may play a role in triggering each of these scenarios, the causes being internal or external to the installation
  • a policy on how to prevent and mitigate major accidents
  • a safety 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 (such as fire-fighting, relief systems and filters) to limit the consequences of any major accident that might occur
  • identification of neighbouring establishments, as well as sites that fall outside the scope of these Regulations, areas and developments that could be the source of, or increase the risk or consequences of a major accident and of domino effects
  • information about the emergency plan for the site, which is also used by the local authority in preparing an external emergency plan

The safety report needs to be kept up to date. If there are any modifications to the plant or the way it is operated or if new facts or information become available that may affect the site risk profile, the safety report must be reviewed and, if necessary, revised at the time. It must be reviewed after five years even if there have not been any changes. The operator must notify the CA of any revision, and also if the five-year review does not lead to a revision.

Prepare and test an internal emergency plan

Upper tier operators must prepare an internal emergency plan to deal with the on-site consequences of a major accident. These plans should be in writing and cover the full range of possible major accidents, including your response to reasonably foreseeable low-probability, high-consequence events, such as catastrophic vessel failure, multiple tank fires following an explosion or a deflagration or detonation within an explosives store.  The details are given in Schedule 4 of the regulations.

Supply information to local authorities for external emergency planning purposes

Local authorities play a key role by preparing, reviewing, revising and testing external emergency plans for dealing with the off-site consequences of major accidents at upper tier sites. To fulfil this role they need information from operators. Operators will need to hold discussions with their local authorities or emergency planning authorities to determine their exact needs.  Details can be found in Regulation 13.

The information for the local authority or emergency planning authority must be supplied no later than the date the internal emergency plan for the site has to be completed.

Provide certain information to the public about their activities

Regulation 17 requires that the CA must make information available to the public in relation to every COMAH establishment.  In order to facilitate this, the CA has set up a web-based system hosted on HSE's website for the provision of public information.
Using this web-based system, operators must provide the information listed in Regulation 17(1) for all establishments. In addition, upper-tier establishments must also provide the information listed in Regulation 17(2). You will need to input the information within a reasonable period of time after your establishment becomes subject to the Regulations, normally no longer than three to four months. Guidance on how to input the information is available on the system.

People who could be affected by an accident at a COMAH establishment must be given information without having to request it. The details are given in Regulation 18, but you should include at least the information required to be made available to the public under Regulation 17.

When you need to provide information

The information for people who could be affected by a major accident at the establishment must be supplied 'within a reasonable period of time after the external emergency plan has been prepared for the establishment'. Six months would be a reasonable time. Link to guidance for requirements and timing.

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