Major accident hazards



The Control of Major Accident Hazards (COMAH) Regulations 2015 aim to prevent major accidents involving dangerous substances and to limit the consequences to people and the environment of any accidents which do occur. The 2015 regulations implement the health and safety requirements of the so-called “Seveso III” European Directive.



The regulations apply to establishments where dangerous substances are present (or likely to be present) in quantities equal to or exceeding the quantities set out in a Schedule to the regulations. HSE explains: “There are two types (tiers) of establishment which are subject to COMAH, known as ‘upper tier’ and ‘lower tier’ depending on the quantity of dangerous substances they hold. Upper tier establishments will hold greater quantities of dangerous substances, meaning that additional requirements are placed on them by the regulations.”


An operator must take all necessary measures to prevent major accidents and to limit their consequences for human health and the environment and demonstrate to the competent authority (such as the HSE or Environment Agency) that it has taken these measures (Regulation 5).



Regulation 6 is concerned with notifications to the Competent Authority (CA). The information that must be sent includes CLP categories (see page 107) of dangerous substances and details about the site surroundings.



Operators must prepare and keep up-to-date a major accident prevention policy (MAPP) (Regulation 7 and Schedule 2). Operators of upper tier establishments must send a safety report to the competent authority demonstrating that all the necessary measures have been taken to prevent major accidents and to limit their consequences to people and the environment. The requirements of safety reports are set out in Regulations 8, 9 and 10. These must be kept up to date. An internal emergency plan must also be prepared, reviewed and tested (Regulation 11 and 12).



A local authority in whose area there is an upper tier establishment must prepare an external emergency plan containing specified information (Regulation 13 and Schedule 4). Regulation 15 contains exemptions to this requirement. The authority must review and test the external emergency plan (Regulation 14) and put it into effect in specified circumstances (Regulation 16).



Regulation 17 deals with the information that must be made available to the public.



Regulation 18 requires an operator of an upper tier establishment to regularly send information to people liable to be affected by a major accident occurring there (without them having to request it) and Regulation 19 requires the competent authority (the HSE or Office for Nuclear Regulation and one of the environment agencies) to adopt a procedure to deal with requests for information. Competent authorities have a range of powers, including imposing duties on groups of establishments, identified as “domino” groups, to co-operate.
Domino groups arise where the risk or consequences of a major accident may be increased because of the geographical position of establishments; their proximity to each other; or the inventories of dangerous substances they hold.