Control of Major Accident Hazards Regulations 2015, UK wide
COMAH Support
COMAH is the heaviest safety regime most operators will ever sit under. The thing that puts a site into it is an inventory calculation rather than an accident. AL23 Safety helps operators work out whether they are in scope, then builds and maintains the duties that follow, for lower tier and upper tier establishments UK wide.
What is COMAH support?
A regime you enter by arithmetic, not by choice
The Control of Major Accident Hazards Regulations 2015, SI 2015/483, came into force on 1 June 2015 and implemented the Seveso III Directive. They apply to an establishment, meaning the whole area under an operator's control where dangerous substances are present in one or more installations. The guidance is L111, third edition, reissued with amendments in October 2015. L111 is guidance rather than an Approved Code of Practice, which surprises people who assume it carries the same legal weight.
COMAH support is the work of establishing your tier honestly, then producing and keeping alive the documents the tier demands. That runs from the notification and the major accident prevention policy at lower tier, through to the safety report, the on site emergency plan and the five year review cycle at upper tier.
Some things sit outside COMAH. Nuclear hazards from ionising radiation, transport of dangerous substances outside establishments, most offshore installations and military establishments are excluded. Getting the boundary right at the start saves a great deal of wasted effort.
Who needs one
Anyone holding dangerous substances near a Schedule 1 threshold
- Chemical manufacturing, formulation and blending sites holding flammable, toxic or oxidising substances
- Fuel and LPG storage and distribution depots
- Cold stores, food and drink plants and abattoirs using anhydrous ammonia refrigeration
- Water treatment works and swimming pool operators holding bulk chlorine
- Agrochemical and fertiliser stores, including sites holding ammonium nitrate
- Explosives and pyrotechnics manufacture and storage
- Anaerobic digestion, biogas upgrading and hydrogen production or storage
- Warehousing and logistics operators storing packaged dangerous goods for third parties
- Any site that has changed its inventory, added a tank or taken on a new customer product since it last checked
The regulations that apply
Your legal framework, in plain terms
COMAH 2015 sits beneath the Health and Safety at Work etc. Act 1974 and is enforced by a joint Competent Authority. Tier is set by comparing your inventory of dangerous substances against Schedule 1, which has two parts. Part 1 lists categories of dangerous substance by CLP hazard classification. Part 2 lists named substances. Where a substance is named the Part 2 figure overrides the Part 1 category figure. Each entry has two qualifying quantities. Column 2 is the lower tier threshold. Column 3 is the upper tier threshold.
Regulation 5, the general duty
Take all measures necessary to prevent major accidents and limit their consequences to people and the environment. Everything else in the regime exists to demonstrate this.
Regulation 6, notification
Notify the Competent Authority using the COMAH notification form, covering the operator, the location, the person in charge, the dangerous substances and quantities, the activities and the immediate environment.
Regulation 7, the major accident prevention policy
A written MAPP, proportionate to the hazards, implemented through a safety management system covering the seven Schedule 2 elements.
Regulations 8 and 9, the safety report and its review
Upper tier only. Schedule 3 sets the content. Regulation 9 sets the review triggers, including a review at least every five years.
Regulations 10 to 13, emergency planning
The operator prepares the internal plan. The local authority prepares the external plan. Both are reviewed and tested.
Regulations 14, 16 and 19
Domino group co-operation, the power to prohibit operation where prevention and mitigation measures are seriously deficient and the Competent Authority inspection system.
How the thresholds actually work
Named substances beat categories
Chlorine qualifies at 10 tonnes lower tier and 25 tonnes upper tier. Anhydrous ammonia qualifies at 50 and 200 tonnes. Hydrogen qualifies at 5 and 50 tonnes. Phosgene qualifies at 0.3 and 0.75 tonnes. Liquefied flammable gases including LPG qualify at 50 and 200 tonnes.
Categories catch everything else
Flammable gases in Category 1 or 2 qualify at 10 and 50 tonnes. Acute toxic Category 1 substances qualify at 5 and 20 tonnes. Ordinary flammable liquids in Category 2 or 3 qualify at 5,000 and 50,000 tonnes. The same liquids held above their boiling point or in other high hazard conditions drop to 10 and 50 tonnes.
The summation rule catches the rest
Where no single substance reaches a threshold, three separate sums are calculated for health hazards, physical hazards and environmental hazards. For each sum, the quantity present is divided by the relevant qualifying quantity and the fractions are added. If any one sum reaches 1, the establishment is in scope at that tier.
Aggregation is where sites get caught out
A warehouse with nothing close to a threshold on its own can be upper tier once the environmental hazard fractions are added together. This is the single most common and most expensive surprise in the regime.
What the service covers
From tier screening to the five year review
- Inventory build and tier screening against Schedule 1 Parts 1 and 2, including the three summation calculations and a written record of the basis
- Notification under regulation 6, plus re notification where the inventory, the activities or the operator change
- Major accident prevention policy drafting, written to the hazards rather than copied from a template
- Safety management system development against the seven Schedule 2 elements, covering organisation and personnel, hazard identification and evaluation, operational control, management of change, emergency planning, performance monitoring and audit and review
- Major accident scenario development, consequence description and the demonstration that measures necessary have been taken
- Safety report authoring and Schedule 3 content mapping for upper tier establishments
- Five year safety report reviews, modification reviews and the notification to the Competent Authority that follows a review
- On site emergency plan writing to Schedule 5, including the employee and long term contractor consultation the regulation requires
- Supply of the information the local authority needs to prepare the off site emergency plan
- Emergency plan testing, exercise design and the review record
- Regulation 17 and regulation 18 public information, including the content and the route by which it is made available
- Domino group information exchange under regulation 14, where the Competent Authority has grouped your site with a neighbour
- Intervention preparation, including assembling the evidence a joint inspection team will ask for
Our process
Screen honestly, then build to the tier
- 01
Screening
We build the inventory from what is actually held rather than what the tank schedule says, run the summation calculations and give you a written tier position you can defend.
- 02
Gap analysis
We test what exists against the duties for that tier, separating documents that are missing from documents that exist but would not survive scrutiny.
- 03
Build
We draft the MAPP, the safety management system elements, the emergency plan or the safety report, working from your hazard studies rather than around them.
- 04
Demonstration
We test the argument the way an inspector would, checking that each claimed measure is real, is maintained and is evidenced.
- 05
Maintain
We set the review cycle, the modification triggers and the exercise programme so the regime keeps running between inspections.
What you get
Documents that survive a joint inspection
- A tier determination report showing the inventory, the qualifying quantities applied and each summation calculation in full
- A completed regulation 6 notification, ready for submission
- A written major accident prevention policy with a safety management system mapped to the Schedule 2 elements
- A safety report or safety report revision mapped clause by clause to Schedule 3, for upper tier sites
- An on site emergency plan to Schedule 5, with a test and review schedule and an exercise record template
- A public information pack meeting the Schedule 4 content requirements
- A prioritised action plan separating legal gaps from improvement points, with owners and target dates
What we need from you
The real inventory, not the average
- A full inventory of dangerous substances with maximum quantities present, not average holdings
- Safety data sheets and CLP classifications for every substance, including customer owned stock
- Site plans, process descriptions and existing hazard studies
- Any previous notification, MAPP, safety report and Competent Authority correspondence
- Access to operations, maintenance and emergency response staff during the work
Why AL23 Safety
The arithmetic shown, the scope owned
Accountable
If the summation puts you in a tier you did not expect, we tell you straight away and we show the arithmetic. Under stating an inventory is not a strategy.
Specialist work, resourced honestly
Upper tier safety report work is a major undertaking and we treat it as one. We scope the work, appoint the right specialist, interpret the results and turn them into an action plan you can actually deliver. The scope and the accountability stay with us.
Joined up with the studies behind it
A safety report is only as strong as the hazard identification underneath, which is why we tie this work to your hazard analysis and to the integrity claims made for your safety instrumented systems.
UK wide
We support COMAH operators across the UK from our Manchester base, on single installations and on multi operator sites.
Talk to us about COMAH
Start with the question that decides everything else
If you are not certain which tier you are in, that is the call to make first. Send us the inventory and we will tell you what the arithmetic says. No obligation and no pressure.
Common questions
Answers, up front
Cannot see your question? Get in touch and we will answer it directly.
Contact usNot HSE alone. COMAH is enforced by a joint Competent Authority. In England that is HSE together with the Environment Agency. On nuclear sites the Office for Nuclear Regulation takes the HSE role. In Wales it is HSE or ONR with Natural Resources Wales. In Scotland it is HSE or ONR with the Scottish Environment Protection Agency. The two bodies act jointly and a single inspection team covers safety and environmental protection together. The Competent Authority has a duty to inspect and can prohibit operation where prevention and mitigation measures are seriously deficient.
At least every five years, even where nothing has changed. A review is also required whenever there is a modification with significant repercussions for major accident hazards, following a major accident at the establishment, where new facts or new technical knowledge justify it, plus any occasion on which the MAPP is revised. After a review you must notify the Competent Authority either of the revisions made or that no changes were necessary.
The range is very wide. A tier screening exercise for a site with a short inventory is a small piece of work. A first safety report for a complex upper tier establishment is a programme measured in months, with scenario modelling and specialist input behind it. Cost follows the number of installations, the number of major accident scenarios and the state of the existing documentation. Tell us the site and the tier and we will scope it properly rather than quote a figure that means nothing.
Yes. Regulation 10 requires the internal emergency plan to cover the full range of possible major accidents, including low probability high consequence events. You must consult employees, including long term contractor staff, when preparing it. Under regulation 12 the plan must be reviewed and tested at suitable intervals not exceeding three years. You must also give the local authority what it needs to prepare the off site plan. Our emergency planning and business continuity page covers how the two fit together.
No. The land use planning requirements of Seveso III are not implemented through COMAH 2015. In England they sit in the Planning (Hazardous Substances) Act 1990 and the Planning (Hazardous Substances) Regulations 2015, SI 2015/627, with parallel Welsh and Scottish instruments. Hazardous substances consent is needed to hold a controlled quantity, normally granted by the local planning authority. HSE is a statutory consultee on development within consultation distances around major hazard sites and pipelines. It either advises against a proposal or does not advise against it. That advice is not binding on the planning authority. A decision to grant against it must be notified to HSE.
Under regulation 17 every operator, lower tier and upper tier, must make the Schedule 4 information permanently available to the public, including electronically. HSE expects this within a reasonable period after the site becomes subject to the Regulations, normally no longer than three to four months. Under regulation 18, upper tier operators must also supply information directly to everyone likely to be affected by a major accident, including schools and hospitals, without them having to ask. That should reach people within a reasonable period after the external emergency plan is prepared. Six months is considered reasonable. The information then has to be kept current and repeated periodically. We confirm those intervals against the regulation for your site rather than quoting a rule of thumb.
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