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


OG status:
Fully open
Author unit / section:
Target audience:
SI Inspectors


This SPC sets out Specialised Industries (SI) 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 SI flexibility to decide which major hazard precursor events to investigate.

Selection criteria

The following criteria should be used:

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 SI sectors there are diverse major hazard precursor events and therefore Annexes 2 to 5 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 HID SI6.

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 e.g. 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, e.g. 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:

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 – Explosives Unit incident selection criteria

The Explosives Unit is responsible for investigating dangerous occurrences:

The mandatory investigation of dangerous occurrences

Only reported dangerous occurrences as defined in Schedule 2 of RIDDOR that are major hazard precursor events will be subject to mandatory investigation.

Major hazard precursor events are those dangerous occurrences where:

Where a dangerous occurrence does not meet these criteria, the incident will not normally be investigated. However initial enquiries (usually made by telephone to determine the full circumstances) may highlight an opportunity to address a specific training need that may be met by an inspector investigating a DO which does not meet these criteria.  In these circumstances, the B2 should mark the incident as "non-mandatory" on COIN whilst forwarding it for investigation.

Annex 4 – Gas & Pipelines Unit incident selection criteria

The Gas and Pipelines Unit is responsible for:

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:

Annex 5 – Biological Agents Unit (HID SI4) incident selection criteria

Frontline regulatory remit of HID SI4

For HID SI4, the types of incidents to which this should be applied must fall within the inspection remit of the unit, as defined in operational circulars (OC349/06 and OC349/10). In essence, this involves biological agents (including human, animal and genetically modified microorganisms (GMMs), which are deliberately handled under contained use conditions. This includes any research activities, all work with GMMs, all work with specified animal pathogens and work in clinical diagnostic containment level (CL) 3 laboratories.

It is also important to recognise that within this frontline regulatory remit, there are a wide range of biological hazards, which are categorised into hazard groups (HG) or activity classes. For the purposes of investigation and inspection, it is imperative to target resources to the greatest hazards and risks. For HID SI4, this primarily means work that involves high hazard biological agents (i.e. HG4, HG3).

Notification requirements

The notification by duty holders of incidents that fall within HID SI4 remit is a requirement of three separate pieces of legislation:

The requirement to notify an incident is based on an assessment of the circumstances surrounding the incident weighed against the incident reporting criteria (in the relevant legislation). Basically, the employer has to decide whether the incident meets the definition within the regulations. This assessment is subjective particularly where there has not been an exposure or actual release of material. Consequently, there is potential for significant under-reporting as well as inconsistent reporting. The precise reporting criteria from the different legislation are not considered in this document.

Incident selection criteria covering major hazard precursor events that affect human health [2]

From a HID SI4 perspective, the activities identified as being equivalent to major hazards should form part of the decision as to whether the incident is considered to be mandatory or non-mandatory for investigation. Thus, the following are mandatory:

Other work involving human pathogen HG3 or GM Class 3 where the organisms are transmitted by vectors, blood borne or ingestion routes, for which full containment level (CL) 3 control measures may be derogated are not considered to be major hazards. Similarly all other human pathogen HG2 and GM Class 2 activities are not considered to be major hazards work. There may be valid reasons to target the non-major hazards elements of biological agents' work, where breaches are recurrent or are deemed significant. However, these incidents are not mandatory for investigation.

Incident selection criteria for contained use activities that affect the environment [3]

Similar to the criteria for incidents that affect humans, the activities identified as major hazards should be used to determine whether the incident is considered to be mandatory or non-mandatory for investigation and where applicable the same criteria apply. Thus, the following incidents are mandatory for investigation:

Other work involving SAPO 3 or Class 3 GMMs where the organism is transmitted by vectors, blood borne or  ingestion routes, for which full containment level (CL) 3 control measures may be derogated, are not considered to be major hazards. Similarly all other SAPO 2 and Class 2 GMMs are not considered to be major hazards work and incidents involving these are not mandatory for investigation. There may be valid reasons to target the non-major hazards elements of contained use work, where breaches are deemed recurrent or significant.

Other considerations

The former not withstanding, all incidents involving contained use work likely to give rise to serous public concern should be considered for investigation. Consider in particular:

Exceptionally, HSE may decide not to investigate where:


  1. The notification requirement is part of the SAPO licence conditions issues under this Order and would include those issued under equivalent Orders in Scotland and Wales.
  2. This will apply to incidents reported under RIDDOR or GMO(CU)
  3. This will apply to incidents reported under SAPO or GMO(CU) where harm is caused to specified animals under SAPO or the wider environment (e.g. animals, plants) under GMO(CU).
Updated 2018-08-15