title: "COMAH Regulations 2015" type: wiki source: legislation.gov.uk url: https://www.legislation.gov.uk/uksi/2015/483 date: 2015-06-01 updated: 2026-04-12 tags: [hse, comah, major-accidents, seveso, safety, lng, gas-storage, hydrogen]

COMAH Regulations 2015

What COMAH Is

COMAH = Control of Major Accident Hazards. The Control of Major Accident Hazards Regulations 2015 (SI 2015/483) set out GB safety law for industrial sites that hold dangerous substances in large quantities - sufficient to cause a major accident if released, ignited, or otherwise lost from control.

The Regulations came into force 1 June 2015 and extend to Great Britain. They replaced the 1999 COMAH Regulations.

Seveso Origin

The Regulations implement Directive 2012/18/EU ("Seveso III"), the third iteration of an EU framework that traces to the 1976 Seveso chemical disaster in Italy and was substantially strengthened after the 1984 Bhopal disaster in India. The Seveso framework has been part of GB industrial safety law since 1982 and is retained EU law post-Brexit.

The Seveso III Directive updated substance classifications to align with the EU's CLP Regulation (GHS classification system) and strengthened public information and inspection requirements compared to Seveso II (1996).

Upper and Lower Tier Distinction

The Regulations create two tiers of obligation based on how much of a dangerous substance is present at an establishment:

Lower-tier: substance present at or above the lower qualifying quantity (Schedule 1, column 2). Obligations: notify HSE, prepare a Major Accident Prevention Policy, demonstrate basic safety management, be subject to inspection.

Upper-tier: substance present at or above the upper qualifying quantity (Schedule 1, column 3). All lower-tier obligations plus: prepare a full safety report, prepare internal and external emergency plans, proactively inform the surrounding population, and pay for competent authority examination time.

An "establishment" is the whole location under one operator's control where a dangerous substance is present above threshold. Where a site holds multiple dangerous substances below their individual thresholds, an aggregation rule applies.

Which Energy Sites Are Covered

Energy sites typically in scope:

LNG import terminals (e.g. Isle of Grain, South Hook, Dragon): LNG is natural gas in liquefied form. The Schedule 1 threshold for liquefied flammable gases and natural gas is 200 tonnes for upper-tier. Large import terminals hold far more and are upper-tier.

Onshore gas storage (salt cavern or depleted field, above-ground facilities): natural gas at operating pressures above the 200-tonne upper-tier threshold. Note: offshore gas storage is excluded from COMAH. Onshore underground storage in natural strata, aquifers, salt cavities and disused mines is explicitly included.

Large petroleum product terminals: motor spirits, kerosines, gas oils (diesel), and heavy fuel oils all fall under Schedule 1 Entry 34. Upper-tier threshold: 25,000 tonnes. Major fuel depots at ports or serving airports are likely upper-tier.

Hydrogen facilities: hydrogen has a low Schedule 1 threshold - 5 tonnes lower-tier, 50 tonnes upper-tier (Entry 15). Almost any significant hydrogen production or storage facility will be COMAH-regulated. As the hydrogen economy scales, many new sites will enter scope.

Some power stations: gas-fired stations are typically below threshold because on-site gas storage is limited. Stations with large fuel oil backup tanks may be lower-tier under the petroleum products entry.

Sites outside scope: offshore platforms and offshore gas storage, nuclear sites (where dangerous substances create a radiation hazard rather than a chemical hazard - those are regulated by ONR under nuclear law), military establishments.

MAPP and Safety Report

MAPP (Major Accident Prevention Policy): required of all operators (both tiers). A written statement of safety aims, management roles, and commitment to continuous improvement. Implemented through a safety management system. Reviewed at least every five years.

Safety report (upper-tier only): the central COMAH document. Must demonstrate that hazards have been identified, prevention measures are in place, safety is embedded in design and operation, an internal emergency plan exists, and the surrounding area can be planned around. Must be submitted before construction and operation can begin. A new establishment cannot start construction until HSE has concluded its examination of the safety report. Reviewed every five years and after any significant change.

Emergency Planning Requirements

Internal emergency plan (upper-tier): operator prepares measures to be taken inside the establishment. Must be tested and reviewed every three years. Worker consultation required.

External emergency plan (upper-tier): the local authority prepares measures to be taken outside the establishment. Based on information provided by the operator. Must be tested and reviewed every three years. Local authority consults operator, Environment Agency, emergency services, NHS, and public.

Both plans must be put into effect without delay if a major accident occurs or if an uncontrolled event could lead to one.

Land Use Planning Interaction

The Seveso III Directive's land use planning provisions are given effect in GB through planning legislation, not these Regulations. The key instruments are the Planning (Hazardous Substances) Act 1990 and the Planning (Hazardous Substances)(Scotland) Act 1997.

In practice: HSE publishes consultation zone maps around COMAH establishments and acts as a statutory consultee for planning applications within those zones. HSE's Land Use Planning (LUP) methodology assigns land use zones based on risk, advising planning authorities on whether proposed development is compatible with proximity to the COMAH site.

For nationally significant infrastructure projects (NSIPs) under the Planning Act 2008, NPS EN-4 (gas supply infrastructure) and NPS EN-2 (fossil fuel generation) both require applicants to demonstrate that COMAH implications have been addressed. New energy infrastructure that is itself a COMAH establishment cannot begin construction until the competent authority has completed its safety report examination - a sequencing issue that can affect NSIP delivery timelines.

HSE and ONR as Competent Authority

For most energy sites: HSE Executive and the relevant environment agency (Environment Agency / SEPA / Natural Resources Wales) act jointly as the competent authority.

For nuclear establishments (as defined in the Energy Act 2013): ONR and the relevant environment agency act jointly. This means that where a nuclear site holds significant quantities of non-nuclear dangerous substances (fuel oil, ammonia for flue treatment), ONR rather than HSE leads on COMAH.

The competent authority has powers to: examine safety reports, prohibit construction or operation where safety measures are seriously deficient, require information, conduct inspections, identify domino groups, and serve prohibition notices. Fees are charged to operators for competent authority functions.

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