The list of dangerous occurrences in Schedule 2 of RIDDOR is designed to obtain information primarily about incidents with a high potential to cause death or serious injury, but which happen relatively infrequently. Collecting the information allows the enforcing authorities to learn about the circumstances and their causes. This provides valuable information which both regulators and business can use to help prevent accidents.
For clarity, the guidance below includes relevant extracts from the Schedule requirements in bold.
Several types of dangerous occurrence require reporting in circumstances where the incident has the potential to cause injury or death. This assessment does not require any complex analysis, measurement or tests, but rather for a reasonable judgement to be made as to whether the circumstances gave rise to a real, rather then notional, risk. Such judgement allows for prompt reporting, and ensures that valuable information is not lost.
Schedule 2 lists three kinds of reportable dangerous occurrence:
These dangerous occurrences apply to all workplaces and include incidents involving, lifting equipment, pressure systems, overhead electric lines, electrical incidents causing explosion or fire, explosions, biological agents, radiation generators and radiography, breathing apparatus, diving operations, collapse of scaffolding, train collisions, wells and pipelines or pipeline works.
The definition covers the collapse or overturning of any lifting equipment, or the failure of any load-bearing part, whether it is used for lifting goods, materials or people. It does not cover the failure of ancillary equipment, such as electric operating buttons or radius indicators, or failures of lifting accessories, such as chains and slings.
Failure in this context refers to components which suffer mechanical breakdown during the normal operation of the lifting equipment, as opposed to accidental or deliberate damage.
Incidents involving cranes must be reported irrespective of the nature of the work being done, and reports must not be restricted to those involving lifting and lowering. For example, a collapse or overturning when a machine is being used for demolition activities must be included.
Lifting equipment includes machinery such as bored piling rigs and percussion piling rigs.
The definition covers the failure of a pressure system (other than a pipeline) with the potential to cause the death of any person. It applies to any such vessel whatever its contents.
Incidents requiring notification due to having ‘the potential to cause the death of any person’. This includes scaldings or burns arising from contact with steam, hot water, other hot liquids, liquors, hot products or hot substances, and immersion in liquids or splashing with toxic chemicals.
Other examples of incidents which might be notifiable as having ‘potential to cause death’ would be those where a person was either struck by, or could have been struck by, a projectile emitted from the failure of a closed vessel or pipeline under pressure. In the event of an explosion, this might be a fixture or component, the vessel or pipeline itself, or a secondary projectile arising from the destruction of structures close to the vessel, for example falling debris such as masonry or window glass, or shrapnel from buildings or other structures.
Overhead electric lines
Examples of the kinds of incident relating to overhead electric lines, which must be notified and reported are:
Electrical incidents causing explosion or fire
Where the failure of an item of electrical equipment (including as a result of accidental damage) results in a fire or explosion, the failure is reportable as a dangerous occurrence if the equipment concerned is rendered unusable for over 24 hours, or if the occurrence was one with the potential to cause the death of any person. The incident is reportable even if the system in which the damaged equipment was installed is put back into service using new equipment within 24 hours. In such a case an assessment should be made of how long a repair to the damaged equipment would have taken had it been attempted.
Repair time does not include incidental time delays such as those associated with travelling to repair plant in remote locations, or with sourcing parts.
except where a fail-safe device or safe system of work prevented any person being endangered as a result of the fire, explosion or ignition.
These dangerous occurrences refer to specific incidents arising in work situations from the use of explosives, and unintentional events at premises where explosives are manufactured or stored. HSE Explosives Inspectors can give you more advice on this.
Severe human infection or illness means illness caused by biological agents in Hazard Groups 3 and 4 as defined in COSHH 2002, Schedule 3. These are set out in the latest edition of the Management, design and operation of microbiological containment laboratories, or are agents classified provisionally by an employer as being in one of those Hazard Groups. HSE has more specialised guidance on how to apply this and other aspects of RIDDOR in the healthcare sector.
Radiation generators and radiography
There are two types of equipment covered here: radiation generators and equipment using radioactive sources (eg gamma ray sources). A radiation generator means any electrical equipment emitting ionising radiation and containing components operating at a potential difference of more than 5 kV.
The processes covered include all types of industrial radiography – such as radiography in fixed enclosures, site radiography, and radiography in closed cabinets. Irradiation of food and processing of products by irradiation are high-dose treatments and this covers panoramic systems as well as self-contained units. In each case, it is the failure of the means for de-energising the radiation generator at the end of the intended exposure period that constitutes the dangerous occurrence.
Incidents where equipment malfunction causes a radioactive source to fail to return to a safe (shielded) position at the end of the intended exposure period are also reportable dangerous occurrences. The sources will commonly be gamma ray sources, but in industrial radiography could be beta ray or neutron sources. The processes covered once again include all types of industrial radiography, and use of gamma irradiation equipment (panoramic or self-contained). The type of equipment must be such that the source goes from a safe state to an exposed state in use, and operation of manual or automatic control systems normally returns the source to its shielded state. Any malfunction affecting the equipment and its control system causing the failure of the source to return to this state at the end of the intended exposure period constitutes a dangerous occurrence.
These incidents must be reported whether or not anyone is exposed to ionising radiation as a result of the incident occurring, other than those incidents which must be reported under the Ionising Radiations Regulations 1999 (IIR). Where a report is required under IRR, there is no requirement to also report under RIDDOR, except in relation to offshore workplaces.
This definition applies to breathing apparatus used under water as well as in contaminated atmospheres or where there may be a lack of oxygen. It refers to a session of use of the apparatus during or immediately before which a malfunction is detected. The malfunction may be present and be detected immediately before the session (including any testing by the wearer immediately before use), or it may occur at some point after the session has started.
The term ‘malfunction’ does not include leakage into a face mask due to a poor fit or a failure caused by an external source, such as damage due to entanglement or falling debris.
Specialist advice is available from HSE Diving Inspectors.
Collapse of scaffolding
The incidents covered here are those involving any ‘scaffold’. This includes any tower, trestle, slung or suspended scaffold.
The figure of 5 metres used in relation to the height of scaffolding refers to the height of the scaffolding itself from its base and not necessarily to the distance between the top of the scaffold and the ground.
Incidents involving the failure of the suspension arrangements of slung or suspended scaffolds are covered if the failure causes a working platform or cradle to fall. Reportable failures of suspension arrangements would include failures of outriggers, roof rigs or suspension ropes or winches.
This dangerous occurrence applies to railways which are not ‘relevant transport systems.’ It therefore applies to collisions between rail-mounted locomotives or trains and other vehicles within factory or dock premises. Incidents on relevant transport systems are covered by Schedule 2, Part 5 and further guidance is available from the Office of Rail and Road. [Link]
These incidents are reportable for all wells, both onshore and offshore, drilled for the exploration or exploitation of oil or gas, including production of coal bed methane for commercial purposes. They also apply to wells drilled in connection with the exploitation of oil or gas, eg those used to support reservoir pressure through water or gas injection.
Reports are required for all blowouts, including those of limited duration.
Reports are required for all incidents where a blowout preventer is closed or a diverter is operated to control an unplanned flow into the well-bore from the adjoining formations, but not where flow is planned as part of an operation. This includes ‘underground blowouts’, where the well fluids flow to subsurface rock formations rather than to the surface. Reports are not required where flow is due solely to variations in the density of fluid across pipe installed in the well bore, an effect commonly known as ‘u-tubing’; nor where it is known that mud previously lost to the formation is subsequently returned, an effect commonly known as ‘ballooning’ or ‘breathing’.
Failures of the primary pressure containment envelope of a well or of safety devices, namely blowout preventers or surface, subsea and subsurface safety valves, should be reported where there is a major loss of pressure integrity requiring immediate remedial action. It is not necessary to report minor leaks or failures found and rectified during routine maintenance, including replacement of worn components. Significant leakages around a well of hydrocarbon gas from shallow formations should also be reported.
All unplanned well intersections, where a well is unintentionally drilled into an existing one, are reportable. ‘Near misses’ should also be reported if normal drilling operations have to be interrupted to take remedial action to reduce the risk of collision.
Pipelines or pipeline works
The incidents listed are reportable for both onshore and offshore pipelines or pipeline works. The following types of pipeline are not covered by these requirements:
The phrase ‘accidental or uncontrolled release’ is not intended to include minor leaks from pipelines, eg small leaks from valve stems, flanges etc. However, sudden or uncontrolled escapes requiring immediate attention or action should be reported.
Examples of reportable damage with the potential for harm would include such things as gouging, denting, buckling etc caused by external interference requiring immediate action. Such damage mayor may not have resulted in any escape of the pipeline contents. Shutdown following discovery of substantial internal or external corrosion, such that it would not be safe to continue operating the pipeline, should also be reported. External coating damage without damage to the underlying substrate would not be reportable.
Examples of reportable occurrences would include movement of offshore pipelines following development of critical ‘spans’ and subsequent instability or displacement due to wave action or boat impact. Occurrences not reportable would include spans detected and rectified as a result of routine inspection activities.
Such occurrences would include landslips, subsidence etc onshore, in the vicinity of pipelines, and similar movement in the seabed.
These incidents do not require a report if they occur at an offshore workplace. They include structural collapses, explosions or fires, releases of flammable liquids and gases and hazardous escapes of substances.
The dangerous occurrences defined in Schedule 2 part 2 do not apply to offshore workplaces.
‘Offshore workplace’ is defined in regulation 2, and includes wells, offshore pipelines and offshore installations associated with the exploitation of mineral resources. Offshore windfarms and other renewable energy installations are not included.
Only structural collapses associated with ongoing construction, maintenance and demolition work are required to be reported under paragraph 23. However, the paragraph 24 requirement to report unintentional collapses of falsework applies whether construction work is taking place or not.
‘Falsework’ means any temporary structure used to support a permanent structure during its erection and until that structure becomes self-supporting.
Explosion or fire
This definition covers serious fires and explosions at work premises. Examples of the type of incident which would be reportable are:
Release of flammable liquids and gases
This definition covers releases of flammable liquids or gases (eg due to the sudden failure of a storage vessel) where the release, if ignited, would cause a major explosion or fire. ‘Flammable’ includes those substances classified as highly flammable or extremely flammable.
Hazardous escapes of substances
The substances covered by this definition may be in any form: liquid, solid (eg powder), gaseous or vapour and may include, eg:
This definition includes incidents which present a fire or explosion hazard (eg combustible powders), but not in relation to releases of flammable liquids or gases, where the relevant thresholds in 26 [link to paragraph 26] are not exceeded.
Examples of the kinds of incident covered by the definition are escapes arising from the failure or breakage of plant, pipes, equipment or apparatus; failures of process control; the operation of a relief valve or bursting disc where the escaping substance is not safely controlled or directed, and spillages from containers and equipment.
Releases from plant etc during the normal course of operation or maintenance (eg during sampling, packaging or draining of lines) that are sufficiently well controlled to ensure that no person is put at risk would not be reportable.
In some cases, the decision as to whether or not an incident is reportable will be straightforward, eg if a person is exposed to a hazardous substance at a level which exceeds established safe limits (eg a Workplace Exposure Limit).
However, most incidents require judgement. Various factors are relevant including: the nature of the substance and its chemical, physical and toxicological properties, the amount which escaped and its dispersal, and whether people were, or could foreseeably have been, exposed to a significant risk as a consequence of the escape.
Industries with specific requirements are: offshore workplaces, mines, quarries and relevant transport systems.
The dangerous occurrences in this part are reportable only if they occur at an offshore workplace. ‘Offshore workplace’ is defined in regulation 2 , and includes wells, offshore pipelines and offshore installations associated with the exploitation of mineral resources. Offshore windfarms and other renewable energy installations are not included.
Some incidents only apply at offshore installations. Note that in this section ‘offshore installation’ includes subsea units, but excludes tied back wells, pipelines and associated apparatus or works within 500m of the installation's main structure, and fixed towers not associated with oil and gas activities.
Specialist advice on reporting requirements offshore is available.
Release of petroleum hydrocarbon
This refers to confirmed unintentional releases of petroleum hydrocarbons. Suspected releases which turn out to be false, eg spurious alarms, are not reportable. To be reportable, releases must also lead to one of the following outcomes:
Fire or explosion
This covers fires or explosions other than those caused by the release of petroleum hydrocarbon, such as:
Release or escape of dangerous substances
This covers releases of substances such as stored chemicals, superheated steam, or H2S where not associated with hydrocarbons.
It will not always be possible to estimate with any accuracy whether a collision could have occurred or what the consequences might have been. HSE is primarily interested to know of incidents in which the dutyholder considers there was a significant risk to the installation.
Subsidence or collapse of seabed
Loss of stability or buoyancy
Full or partial evacuation may be a response to an incident separately reportable under RIDDOR (eg a fire or explosion), in which case it is not reportable under this paragraph. This definition seeks to include incidents not otherwise reportable, in which the risks are sufficient to warrant evacuation. It does not cover exercises or precautionary measures.
Falls into water
HSE Mines Inspectors can give specialist advice on dangerous occurrences reportable in mines.
HSE Quarries Inspectors can give specialist advice on dangerous occurrences reportable in quarries.
Relevant transport systems
Dangerous occurrences in relevant transport systems are reportable to the Office of Rail and Road, who publish their own guidance on RIDDOR.