The key UK statistics on COMAH major accident hazard sites — how many establishments there are, how they split into tiers, how often they are inspected and what the Competent Authority charges — drawn from HSE’s annual accounts, its Business Plan and the live public registers, and fully sourced.
At the very top of the chemical-safety pyramid sit Britain’s major accident hazard sites: the oil-storage depots, chemical works, gas terminals and warehouses holding dangerous substances in bulk quantities that trigger the Control of Major Accident Hazards (COMAH) Regulations 2015. This page pulls together the key COMAH statistics — establishment counts, tier splits, inspection volumes, cost-recovery fees and enforcement performance — from the Health and Safety Executive’s (HSE) Annual Report and Accounts, its Business Plan, the official fees-and-charges rates and the live GB and Northern Ireland public registers. Every figure carries its data period, and every source is linked at the end.
This page distinguishes establishment counts, planned regulatory work, completed assessments and cost recovery. These measures describe the regulation of major hazards; they are not annual accident counts or proof that an individual site is safe. Historical incidents illustrate why prevention and emergency planning matter. Everyday hazardous-substance duties are covered in our COSHH Regulations 2002 and COSHH statistics guides.
Key facts and figures
- 51 COMAH sites were reported in Wales in 2024: 24 upper tier and 27 lower tier (Natural Resources Wales Annual Regulation Report 2024).
- 1,600+ major hazard installations were described in HSE’s 2025/26 Business Plan — a broader population than COMAH alone.
- 28 COMAH establishments appear on Northern Ireland’s public list checked on 15 October 2026: 10 upper tier and 18 lower tier.
- £218/hr is the Competent Authority’s COMAH cost-recovery rate from 1 April 2026, up from £212/hr (HSE fees and charges).
- 500 onshore major-hazard inspections and 67 COMAH safety-report assessments were indicative planned volumes for 2025/26, not completed inspection totals.
- £8.93m of HSE COMAH fee income against £10.13m of HSE costs in 2024/25 — a £1.20m deficit in the audited accounts.
- 85% of major-hazard safety reports due in 2025/26 were assessed on time: 158 of 186, across COMAH, offshore and gas safety combined (provisional HSE KPI report).
- 28 workers were killed at Flixborough in 1974 — the disaster that built the UK’s major-hazard regime (HSE case study).
Checked on 15 October 2026. Sources cover different periods: the public registers are current snapshots, HSE’s fee accounts cover 2024/25, its indicative plan covers 2025/26, and the provisional KPI report gives completed 2025/26 performance. Each measure retains its own date and scope.
How many COMAH sites are there in the UK?
The HSE public register identifies upper-tier and lower-tier COMAH establishments in Great Britain. Its membership can change as inventories and businesses change, so use the live register to check a specific location. A verified national snapshot is available for Wales: Natural Resources Wales reported 51 COMAH sites in 2024, comprising 24 upper-tier and 27 lower-tier sites. This is a Welsh count, not a Great Britain total.
HSE’s 2025/26 Business Plan described more than 1,600 major hazard installations. That broader regulatory population must not be equated with COMAH establishments alone. Offshore installations, pipelines and explosives also involve distinct regulatory regimes. The offshore hourly rate below is shown as a comparison, not as a COMAH charge.
The regime dates from 1 June 2015, when the COMAH 2015 Regulations came into force, implementing the EU Seveso III Directive and replacing the earlier COMAH 1999 rules. A defining feature is transparency: the public register lets anyone search for establishments within three miles of a postcode, so residents, emergency planners and land-referencing firms can see the major-hazard sites near them.
What is the difference between upper and lower tier COMAH sites?
Two tiers divide the COMAH population, set by the quantity of dangerous substances a site holds against the thresholds in the regulations. Upper-tier sites hold the larger inventories and carry the heaviest duties; lower-tier sites are above the entry threshold but below the upper-tier one, and carry a lighter — though still substantial — set of obligations. The headline difference is the safety report. Upper-tier operators must produce and submit a written safety report demonstrating that all necessary measures have been taken to prevent major accidents and limit their consequences, and that report is formally assessed by the Competent Authority. Lower-tier operators do not submit a full safety report but must still prepare a major accident prevention policy (MAPP) and show it is being implemented. Both tiers must notify their establishment, take all measures necessary to prevent major accidents, and co-operate with emergency planning.
Upper-tier sites also carry the emergency-planning burden in full: the operator prepares an internal plan, the local authority an external plan for the surrounding area, and the public must be given information on how to respond. The tier split is why a single “COMAH site” label can mean very different things — from a modest lower-tier warehouse to a major upper-tier refinery.
How often are COMAH sites inspected?
COMAH Regulation 25 normally requires no more than one year between routine inspections of upper-tier establishments and three years for lower-tier establishments, unless a systematic appraisal of major-accident hazards justifies a different interval. HSE’s 2025/26 plan separately listed indicative volumes of 500 onshore major-hazard inspections, 67 COMAH safety-report assessments and 1,100 follow-up issues, with a target to close 75% of those issues by their due date. Planned volumes are not outturns.
HSE’s 2025/26 plan also included indicative volumes of 8,500 land-use planning applications processed through its web application and 80 hazardous substance consent consultations. These are regulatory planning activities around major hazards, not counts of new COMAH sites or accidents.
An upper-tier safety report must be reviewed at least every five years and at other specified triggers. Internal and external emergency plans must be reviewed and tested at intervals not exceeding three years. These duties are separate from the inspection programme and do not remove the need to respond promptly to changes or deficiencies.
What does COMAH regulation cost? Fees and cost recovery
£218 an hour is what the Competent Authority charges for regulatory activity at COMAH sites from 1 April 2026, up from £212/hr in 2025/26. COMAH runs on full cost recovery: operators pay for the regulator’s time on assessments, inspections and follow-up, rather than the taxpayer footing the bill. For comparison, the equivalent rate for offshore installations is higher still at £332/hr — quoted here only as a rate comparison, since offshore is outside COMAH’s onshore scope.
HSE’s audited 2024/25 accounts record COMAH income of £8.926 million and costs of £10.127 million, a £1.201 million deficit. HSE principally attributes the deficit to staff turnover and experienced staff being replaced by trainees. The prior-year figures were £9.240 million income and £9.457 million costs. These are HSE’s reported finances, not necessarily the combined expenditure of every environmental regulator in the Competent Authority.
| HSE COMAH cost recovery | 2023/24 | 2024/25 |
|---|---|---|
| Fee income | £9.24m | £8.93m |
| HSE costs | £9.46m | £10.13m |
| Surplus / (deficit) | (£0.22m) | (£1.20m) |
| Hourly rate (from following April) | £212/hr (2025/26) | £218/hr (2026/27) |
Figures from HSE Annual Report and Accounts 2024/25 (audited) and HSE fees and charges; hourly rates take effect from 1 April of the year in brackets.
How well does the regulator meet its targets?
HSE’s provisional annual KPI report records 158 of 186 major-hazard safety reports assessed within their due date in 2025/26, or 85%, against a 75% target. This combines COMAH, offshore and gas-safety work; it is not a COMAH-only percentage. HSE says these performance results remain provisional until its annual report is published.
Timeliness helps explain regulatory delivery, but it does not measure the number of accidents prevented or establish that all controls at a site are adequate. Read the completed KPI results separately from indicative planned activity, and assess site-specific prevention measures, safety reports and emergency arrangements on their own merits.
How is Northern Ireland’s COMAH regime different?
Northern Ireland’s DAERA public information list, checked on 15 October 2026, contains 28 establishments: 10 upper tier and 18 lower tier. This is separate from Great Britain. HSENI and NIEA act together as the Competent Authority under Northern Ireland’s own COMAH Regulations 2015.
The framework is materially the same as Great Britain’s — the tier thresholds, the safety-report duty, the emergency-planning obligations and the public-information requirement all mirror the GB rules, both deriving from the Seveso III Directive. The NI count, like the GB one, drifts as establishments enter and leave scope, so re-check it against the DAERA public list on each refresh.
Which landmark major accidents shaped UK regulation?
At Flixborough on 1 June 1974, an explosion killed 28 people and injured 36 on site, with a further 53 reported injuries off site. HSE’s case study describes the failure of a temporary bypass and the release of cyclohexane. It is a historical case illustrating major-accident prevention, not an entry in a current annual COMAH accident total.
At Buncefield on 11 December 2005, fuel escaped from an overfilled storage tank and a vapour cloud ignited. More than 40 people were injured and there were no fatalities. HSE records almost £10 million in fines and costs against five companies. The investigation informed measures for fuel storage, overfill prevention and emergency planning; these historical consequences are distinct from current regulatory activity statistics.
The key numbers at a glance
Eight dated measures show the scope of major-hazard regulation. National snapshots, planned work and delivered performance use different populations and should not be added together.
| Measure | Figure | Data period |
|---|---|---|
| COMAH establishments, Wales | 51 (24 upper / 27 lower) | 2024 |
| Major hazard installations regulated by HSE (all types) | 1,600+ | 2025/26 Business Plan |
| COMAH establishments, Northern Ireland | 28 (10 upper / 18 lower) | DAERA list, 15 Oct 2026 |
| COMAH cost-recovery rate | £218/hr | From 1 Apr 2026 |
| Planned onshore major-hazard inspections | 500 | 2025/26 |
| Planned COMAH safety report assessments | 67 | 2025/26 |
| Major-hazard safety reports assessed by due date | 85% (158 of 186) | 2025/26, provisional; combined regimes |
| HSE COMAH fee income versus costs | £8.93m vs £10.13m | 2024/25 |
Where do these figures come from?
The sources combine HSE’s audited annual accounts, indicative business-plan volumes, provisional KPI results, current fees and the public establishment registers. Natural Resources Wales also reports a dated Welsh establishment count. The date and geographical scope beside each measure are essential to interpreting it.
A register snapshot counts listed establishments, while a business plan describes intended work and a KPI report records delivery against targets. None of those measures should be presented as an accident rate. Use the live registers for the status of a particular establishment and the dated reports for reproducible historical comparisons.
Frequently asked questions
How many COMAH sites are there in the UK?
Use HSE’s public register for Great Britain and DAERA’s public list for Northern Ireland. The latter contained 28 establishments on 15 October 2026: 10 upper tier and 18 lower tier. Natural Resources Wales separately reported 51 Welsh COMAH sites in 2024, comprising 24 upper and 27 lower tier; that is not a Great Britain total.
What is the difference between upper tier and lower tier COMAH sites?
The tier is set by the quantity of dangerous substances a site holds. Upper-tier sites hold larger inventories and must submit a written safety report that the Competent Authority assesses, plus full emergency-planning and public-information duties. Lower-tier sites are above the entry threshold but below the upper-tier one; they prepare a major accident prevention policy instead of a full safety report, but still carry substantial duties.
How often are COMAH sites inspected?
Routine inspection intervals normally must not exceed one year for upper-tier and three years for lower-tier establishments unless a systematic appraisal justifies a different interval. Separately, upper-tier safety reports must be reviewed at least every five years and emergency plans reviewed and tested within three years. The 500 inspections and 67 assessments in HSE’s 2025/26 plan were indicative volumes, not completed totals.
Which landmark major accidents shaped UK regulation?
Flixborough in June 1974 killed 28 people and injured 36 on site and 53 off site. Buncefield in December 2005 injured more than 40 people, with no deaths; five companies incurred almost £10 million in fines and costs. These are dated historical case studies, not a ranking or annual accident count.
Related guides
- COSHH Statistics UK: Hazardous Substances at Work
- Silica Dust Statistics UK: Exposure, Silicosis & Deaths
- Occupational Dermatitis Statistics UK: Work-Related Skin Disease
- COSHH Regulations 2002: A Plain-English Summary
- COSHH Storage Requirements: How to Store Hazardous Substances
Sources & references
- HSE Annual Report and Accounts 2024/25, Table 23
- HSE Business Plan 2025/26: indicative volumes
- HSE provisional KPI report 2025/26
- HSE current cost-recovery rates
- HSE COMAH public register
- DAERA Northern Ireland COMAH list
- Natural Resources Wales Annual Regulation Report 2024
- COMAH 2015 Regulation 25: inspections
- HSE L111: COMAH duties, reviews and emergency plans
- HSE Buncefield investigation
- HSE Flixborough case study
COMAH sits at the top of the same pyramid as everyday hazardous-substance duties — make sure your team understands COSHH before they ever meet the major-hazard end of the scale.
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Mark writes about workplace health & safety, COSHH and accredited online training for COSHH Training, part of Online CPD Academy.