Energy Division selection criteria for investigating major hazard precursor events from 1 October 2010


OG status:
Fully open
Author unit / section:
Energy Division
Target audience:
Relevant Inspectors in Energy Division


This SPC sets out Energy Division's selection criteria for investigating major hazard precursor events under HSE's revised incident selection criteria 1 October 2010 and Annex 1.


In June 2010 HSE Board agreed amendments to HSE's RIDDOR Incident Selection Criteria with effect from 1 October 2010. This included major hazard precursor events, referring to HSE's business plan and relevant workplan for each Operational Directorate. This gives ED flexibility to decide which major hazard precursor events to investigate.

Selection criteria

The following criteria should be used:

  • Incidents that result in or have the potential for significant releases of dangerous substances
  • Incidents that could be precursors to major incidents
  • Incidents that indicate that duty holders are not adequately controlling major hazards.

The range of potential precursor events covered by these criteria is broad and it is important that the criteria are not limiting, allowing the significance of each event to be judged based on its individual circumstances and characteristics.

It is also important that the trigger for investigation should not be wholly based on consequence (actual or potential) but also on the significance of the control measure failure that gave rise to the incident.

Across ED sectors there are diverse major hazard precursor events and therefore Annexes 2 and 3 provide further guidance on selecting incidents for investigation within the above framework.


The criteria should be used when making decisions whether to investigate RIDDOR major hazard precursor events.

Where the selection criteria are met, the expectation is that the incident should be investigated. Where a decision not to investigate is taken, the reasons for not investigating should be recorded on COIN, including completion of a Decision Recording Form (DRF). See COIN reference guide.

Further information

Can be obtained from ED Divisional Support Team.

Annex 1 – Revised incident selection criteria 1 October 2010

Criteria for selection for investigation of RIDDOR notifications (except gas incidents reported under Reg 6(1) and 6(2))

Fatalities - All fatalities as a result of an incident arising out of or in connection with work activities. This specifically excludes suicides* and deaths from natural causes.

* In some circumstances eg in health or social care, the risk of suicide may arise from the work activity in which case HSE guidance on the application of HSWA section 3 should be applied.

Injuries to all persons, including non-employees, irrespective of cause that meet the following conditions:

  1. all amputations of digit(s) past the first joint;
  2. amputation of hand/arm or foot/leg;
  3. serious multiple fractures (more than one bone, not including wrist or ankle);
  4. crush injuries leading to internal organ damage, eg ruptured spleen;
  5. head injuries involving loss of consciousness;
  6. burns and scalds covering more than 10% of the surface area of the body;
  7. permanent blinding of one or both eyes;
  8. any degree of scalping; and
  9. asphyxiations

RIDDOR (schedule 1) defined major injuries arising from working in a confined space or an electrical incident.

Occupational diseases All reports of cases of occupational disease which meet the criteria of reportability under RIDDOR, except those arising from circumstances/ situations which have already been investigated.

Serious breach of health and safety law including incidents likely to give rise to serious public concern where, in accordance with the Enforcement Management Model, the national enforcement expectation would determine a notice or a prosecution.

Major hazard precursor events as identified within HSE's business plan and relevant workplan for each HSE Operational Directorate.

Annex 2 – Mines Unit incident selection criteria

The mandatory investigation of dangerous occurrences

These notes supplement the 'revised incident selection criteria 2010' document that forms part of HSE's operational procedures for investigation.

In addition to selected mines dangerous occurrences listed in Part II of Schedule 2 to RIDDOR, the attached table 1 also lists selected 'general' dangerous occurrences found in Part I of the schedule, along with two from Part IV relating to trains. For the purposes of RIDDOR 'trains' can be taken to include cableways.

The 'investigation' column lists the default expectation of whether an investigation should be undertaken. Where the indication is 'yes' but initial enquiries suggest that an investigation is not warranted, then this should be discussed with the Chief Inspector. If, after discussion, a decision is made not to investigate then the reasons should be recorded on a decision recording form (DRF), which should then be attached to a note on the COIN case.

HSE's investigation guidance gives the following examples of factors that may lead to a decision not to investigate:

  • investigation is impractical, eg due to the unavailability of key witness(es), key evidence is no longer available
  • no reasonably practicable precautions are/were available to prevent the incident or to prevent recurrence of the incident
  • inadequate resources or other developing priorities prevent investigation

Where a dangerous occurrence is not listed but initial enquiries suggest that an investigation is warranted, then the inspector should discuss this with the Chief Inspector. If, after discussion, a decision is made to investigate then the reason(s) for undertaking the investigation should be recorded in the text field of a COIN case note.

Table 1
RIDDOR Reference Brief description Investigate Notes
Schedule 2 Part I
5 Electrical short circuit (as defined) Yes If underground at a safety lamp mine
20 Escape of flammable substances Yes Subject to quantities defined in RIDDOR (see also 2/II/23)
21 Escape of substances (as defined) Yes  
Schedule 2 Part II
22 Fire or ignition of gas or dust U/G Yes Coal mines only
23 Accidental ignition of gas on surface Yes Subject to quantities of flammable substance defined in 2/I/20)
24 Outbreak of any fire below ground Yes Coal mines only
27 Outburst of gas Yes  
28 Breakage of part of winding system Yes  
29 Breakage/uncoupling on mass transport system Yes  
30 Overwinds Yes  
32 Collapse of headframe, winding engine house, fan house or storage bunker Yes Involve construction specialists.
34 Injury by explosion of blasting material Yes  
36 Inrush of noxious or flammable gas Yes  
37 Inrush of water Yes  
38 Insecure tips Yes If potential for offsite danger
39 Locomotives Yes If locomotive hauling passenger vehicles, other than when shunting
40 Falls of ground Yes  
Schedule II Part IV
54 Train (cableway) striking buffer stop Yes If damage caused to vehicle
59 Failure of train parts (as defined) Yes  

Annex 3 – Gas & Pipelines Unit incident selection criteria

The Gas and Pipelines Unit is responsible for:

  • Offshore pipelines – used to transfer oil and gas extracted via offshore installations. Emergency Shut Down Valves (ESDV) associated with pipeline risers are also included within this area of responsibility;
  • Onshore pipelines – used to transport gas and other fluids across the country;
  • Gas importation, processing and storage – including sub-sea pipelines and interconnectors, gas processing at beach terminals, Liquefied Natural Gas (LNG) terminals fed from sea-going vessels, gas holders and gas held in salt cavities. This includes a number of top and lower tier COMAH establishments; and
  • Emerging energy sources – including biomethane generated by the anaerobic digestion of organic waste, coal bed methane, underground coal gasification and transportation of captured carbon dioxide.

The unit is not responsible for enforcement relating to gas use downstream of meter connections, nor for LPG usage.

The following incidents will be subject to mandatory investigation procedures, in addition to the HSE-wide mandatory investigation criteria:

  • Other Riser ESDV failures (eg failures identified as part of routine maintenance or testing) may be investigated as part of other interventions, but investigation is not automatic.
  • Onshore pipelines – any incident involving a Major Accident Hazard Pipeline reported under RIDDOR Schedule 2 Part 1 14 (a) and (g)
  • Onshore pipelines and other relevant installations - any incident reported under RIDDOR Schedule 2 Part 1 14 or any other provision where a fire or explosion resulted from the ignition of a release of gas or flammable vapour.

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Updated 2020-12-09