Inspection of gas supply emergency arrangements and associated co-operation requirements


This guidance outlines the key areas to include, and ratings to apply, in inspections of gas supply emergency arrangements and associated co-operation requirements. It does not cover gas supply emergencies on networks outside the scope of the Gas Safety (Management) Regulations 1996 (GSMR) (as amended).


A gas supply emergency arises from a loss of pressure in the GB gas supply network or any part of it. There are two types:

  • a Network Gas Supply Emergency (NGSE) occurs on a national scale and may result in insufficient gas supplies being available to the National Transmission System (NTS)
  • a Local Gas Supply Emergency (LGSE) may affect part, or all, of a specific gas distribution network (GDN) and networks fed by it. An LGSE may be associated with a wider NGSE, or may arise from and affect just one GDN.

In either case, gas supplies to a significant number of consumers may need to be isolated and subsequently restored. The major hazard implications of this are twofold:

  • during cold weather, vulnerable people (eg the elderly) who rely on gas to heat their homes may be at risk of hypothermia
  • poorly controlled gas supply isolation and restoration operations carry a fire and explosion risk. This is why domestic consumer self-isolation and restoration processes, where considered for use during cold weather, must be subject to strict governance arrangements. Further information on this topic is available on HSE's website

Robust and effective industry arrangements that involve co-operation and co-ordination between a number of different parties are needed to prevent or manage both NGSEs and LGSEs. These arrangements need to be rigorously rehearsed and tested to ensure that the response to a real gas supply emergency will be timely and effective.

This guidance provides inspectors with a framework to judge compliance, assign performance ratings and decide what enforcement action is necessary should legislative breaches exist. It complements and supports HSE's Enforcement Management Model (EMM) and Enforcement Policy Statement. It should be used to inspect any of the following:

  • conduct and review of emergency exercises, both locally and nationally
  • preparedness (including training and competence assurance) outside of exercises
  • implementation of arrangements following a genuine gas supply emergency
  • restoration of supplies after an NGSE, localised incident or LGSE
  • authorisation and use of consumer self-isolation and restoration processes during cold winter conditions in any gas supply emergency
  • verification of safety case changes.


The purpose of inspections of industry gas supply emergency arrangements is to check compliance and issues relevant to the:

  • prevention and management of such emergencies; and
  • associated dutyholder co-operation arrangements.

During inspections of emergency exercises, inspectors should:

  • Check the key issues against the success criteria in those appendices which apply:
    • Appendix 1 Supply emergency arrangements
    • Appendix 2 NEC emergency exercises
    • Appendix 3 Standalone LGSE emergency exercises
    • Appendix 4 Co-operation arrangements for supply emergencies
  • Determine the EMM initial enforcement expectation and assign a performance rating using the scoring table in Appendix 5
  • Consider how and when the issues raised during an inspection are to be recorded using the COIN issues tab and closed out
  • Monitor ongoing matters of concern including:
    • accuracy of large site contact information
    • ability/inability/refusal of sites to turn off gas
    • identification of declared priority users (via Department for Energy Security and Net Zero)


National Gas Transmission (NGT) is the operator of the National Transmission System (NTS), Great Britain's primary gas transmission system, and acts as the Network Emergency Coordinator (NEC). The NEC is responsible for co-ordinating actions across the affected parts of the network to prevent a NGSE developing. If preventative action is not effective, the NEC must take timely decisions in order to minimise the safety consequences of the NGSE. This is likely to include load shedding, where major gas users are taken off gas to reduce demand on the system. Cooperation with the NEC, by gas conveyors and others, is central to the success of the NEC's actions at every stage of the emergency.

Individual Gas Distribution Networks (GDNs) and Independent Gas Transporters (IGTs) take primary responsibility for the prevention, or minimisation of the effects of, LGSEs affecting their networks. The NEC takes no part in the management of a LGSE that is not a result of a NGSE. Appendix 6 gives further information on the types and classification of gas supply emergencies and the role of the NEC is described in more detail in Appendix 7.

Emergency Exercises

Emergency exercises aim to ensure emergency arrangements and preparedness are robust and that dutyholders are aware of, and are able to discharge, their responsibilities.

NEC emergency exercises

These rehearse and test the actions required by the NEC in the event of an NGSE. GSMR co-operation requirements are also tested. The NEC arranges emergency exercises every year, this is a requirement of their safety case.

Exercises vary in scope and scale each year but typically include at least one national exercise (which is advised to NEC inspector well in advance) and possibly one or more internal exercises. The exercises are organised on behalf of the NEC by the emergency planning team at NGT. The annual exercise is usually held in September or October during normal working hours. The NEC issue a briefing pack 2-3 months beforehand to exercise participants listed in Appendix 8. The annual exercise is either run over 1-3 consecutive days or is split up into separate days to test different aspects of the response to an NGSE.

Where the NEC issues Urgent Communication Notices as part of the exercise (for example, exercise start/end, emergency stage declarations), they should be sent to HSE’s GSMR email: [email protected]. The exercise lead inspector should advise the administration team that these are expected to arrive.

Following a national exercise, the NEC and each GDN produce a performance report with the aim of identifying areas for further improvement. These reports, which are sent to HSE, are typically included in HSE's inspection process.

GDN Standalone LGSE emergency exercises

To comply with its safety case a GDN is obliged to run exercises to rehearse and test the actions required by them in the event of a supply emergency arising on its own distribution network and networks affected by it. This is distinct from a LGSE arising as part of an NGSE.

There is no set frequency to testing standalone LGSEs. A GDN may test in isolation from other GDNs or in conjunction with one or more of them for example, to test mutual aid arrangements. The lead inspector for a GDN will need to discuss LGSE emergency test planning with that GDN in order to establish timing, briefing, inspection and reporting requirements.



Inspections should be carried out in accordance with the intervention plans for NGT (if it covers the NEC) or the separate NEC intervention plan the GDNs and the IGTs. The risk ranking arrangements used by ED5 may also be used to decide intervention frequency and targeting of dutyholders.

Other dutyholders who do not have GSMR intervention plans can play a crucial part in emergency exercises and may require an intervention if found to be in breach of their legal duties, such as:

  • Shippers whose poor consumer contact information indicates a failure to adequately co-operate with the NEC
  • Large consumer sites who refuse to cease using gas during load shedding in a real LGSE, as opposed to an exercise
  • Others whose poor response in an exercise indicates a failure to adequately co-operate with the NEC eg network entry facility operators, storage facility operators


Inspection of NEC-led emergency exercises should be timed to coincide with:

  • periodic (usually annual) full scale exercises
  • communications exercises
  • strategy exercises

There is no set frequency for GDNs to test standalone LGSEs and Inspectors should request test schedules from the dutyholder.


Depending on intervention planning priorities, ED3 inspectors will inspect NEC-led exercises centrally and also inspect at one or more GDNs.

Recording and Reporting

Ratings against the NGT or NEC (if separate intervention plans) other GDNs and IGTs should be made using the Inspection Rating Form (IRF) tab of the Intervention Plan Service Orders (IPSOs) for 'Prevention and management of gas supply emergencies' and 'Co-operation arrangements'. Ratings should reflect an EMM risk gap assessment based on the degree to which the success criteria outlined in the Appendices 1 to 4 are met.

Inspectors may also encounter the following topics during an inspection covered by this guidance and these should be rated separately:

  • Safety Leadership
  • Safety Performance Indicators
  • Gas escape arrangements
  • Competence


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Updated 2024-04-03