Cause and Prevention

PAUL RANDALL AND ASSOCIATESHealth and safety Training

CAUSES AND PREVENTION OFCAUSES AND PREVENTION OFCAUSES AND PREVENTION OFCAUSES AND PREVENTION OFCAUSES AND PREVENTION OFACCIDENTSACCIDENTSACCIDENTSACCIDENTSACCIDENTS

NEBOSH Certificate: 6.3.1, 6.3.2, 6.3.3

Causes and prevention of accidents

1 Immediate and underlying accident causes ...................................... 5

2 Accident triangle / pyramid / iceberg ................................................. 72.1 Heinrichs and Birds accident pyramids ................................... 7

3 Domino theory (single-causal) ........................................................ 103.1 Heinrichs domino theory ........................................................ 103.2 Bird and Loftus domino model ............................................... 12

4 Multiple-causal accident models ..................................................... 13

5 Unsafe acts and unsafe conditions ................................................. 15

6 Classification of accidents ............................................................... 17

7 (Pro)active and reactive monitoring of h and s performance ......... 188 Safe person and safe place strategies ............................................ 19

9 Five steps to a safe system of work ................................................ 21

Syllabus coverage 6.3.1 The principles of accident prevention and the main causes of

accidents 6.3.2 The differences between immediate and root (underlying)

causes of accidents 6.3.3 The concepts of safe place (for example: safe workplace,

equipment, environment); and safe person (personal protectiveequipment, information, instruction, training, safe behaviour)


424 Stirling Road, Chichester, PO19 2ES01243 776394 paulrandallandassociates.com



1 Immediate and underlying accident causesIn the part of the examination dealing with the management ofsafety, NEBOSH will often ask questions such as ...

Question X ... describe the immediate and underlying (root) causesof an accident in which an operators clothing is caught ...

Question Y ... with reference to an accident of your own choosing,describe the immediate and underlying (root) causes.

Two typical NEBOSH Certificate accident causes questions

If, as with Question X, a specific accident is provided, NEBOSHwill ensure that the situation in question is straightforward andunderstandable to all students.Very often, the question will be of the second type above (... yourown choosing ...) and you should ensure that you are well-prepared to provide an answer; clearly you will be able to choosebetween a major accident which you have seen on television orread about in the journals or a much less dramatic accident fromyour own experience.Dont feel that more marks are available for a discussion of (say)the Chernobyl catastrophe rather than a minor accident of yourown experience - NEBOSH encourage you to relate your studiesto your own work experience and here is a good opportunity.Accordingly, we urge you to prepare an appropriate from yourown experiences answer and submit it to the Chichester centrefor discussion.



In general terms, the NEBOSH examiners will be looking for thefollowing distinctions between immediate and underlying causes:

Root causeinadequacies in the system thatallow the immediate causes toarise and lead to an accident :inadequate training and instruc-tion in the use of equipmentpoor maintenanceunsatisfactory systems of workfailure to conduct appropriate riskassessments and inspectionsinadequate staff selectionunrealistic demands and expecta-tions placed on the staff leadingto stress and corner-cutting

Immediate causesubstandard acts or conditionswhich lead directly to the accident :removal of, or damage to, a guardoperator errornot wearing ppe (helmet, gloves,boots, rpe)lack of concentrationstress / fatigue / drugspoor housekeeping (build-up oflitter, spillages)

You can probably add items to the table above. At times you mayfind it difficult to know whether to classify a particular cause asbeing immediate or root; for example the stress experienced by aworker suffering in silence which led to an accident may be saidto be immediate and personal in the sense that it arose from, say,a bereavement. Alternatively the stress in question might be bestdescribed as institutional with just about everyone in the work-place overstressed.Clearly, a sympathetic and well-organised workplace should beable to cope with the bereaved worker, supporting him or her,whilst ensuring that no-one is put at risk.In their quarterly reports, the NEBOSH examiners have some-times noted that, when answering accident causes questions,few students support their answers with basic accident causationtheory. Accident theory is a natural extension of what we havelooked at so far, and accordingly, this is where we will now turn(sections 2, 3 and 4).



2 Accident triangle / pyramid / icebergShortly after the Piper Alpha disaster, there was another oil rigfire which resulted in the death of the radio operator. As theshocked survivors were brought to shore, a reporter asked oneman when did you realise that something was wrong?. I clearlyremember his embittered response: about six months ago. Thischilling claim brought vividly to mind the feeling of a whole weightof factors pushing inexorably towards an accident, with one finalcapricious throw of fates dice determining the if, the when, andthe what of the outcome.Starting in the early years of the last century, various models havebeen developed to explain the factors behind, and the build-up to,an accident. Some models were developed by industrial organi-sations, keen to maximise their efficiency, some as part of thegrowing interest in the (then) new subjects of psychology / humanbehaviour.One of the models that established itself most strongly was that ofHeinrich who claimed that:

... for every mishap resulting in an injury, there are many accidentsthat cause no injuries at all.

Heinrich 1931

2.1 Heinrichs and Birds accident pyramidsHeinrich estimated that, in a group of 330 accidents, 300 result inno-injury, 29 in minor injuries, and 1 in major lost-time injury. In asubsequent analysis of nearly 100,000 actual incidents over aseven year period, Bird discovered that for every 1 disablinginjury there were 100 minor injuries and over 500 property dam-age accidents.More important than the differences between these tip of theiceberg models of Bird and Heinrich (in any case, their method-ologies differ in several details) are the overall principles whichthey encompass.You should note that these iceberg models are sometimes alsocalled accident pyramids or accident triangles - not to be con-fused with the fire triangle.



As an aside, here is another example of the accident iceberg ortriangle ...The following was taken from a recent issue of the useful CronerHealth and Safety Briefing. (For your interest, we have alsoincluded a little more of the article, about levels of fines etc.)

Local authority report

The Health and Safety Executive (HSE) has published the latestHSE/Local Authority Enforcement Liaison Committee (HELA)annual report, giving health and safety statistics for work activitieswhere the local authority is the enforcement agency.

The provisional figures for injuries reported in the year 1999/2000include:

* 11 work-related fatal injuries to employees (12 last year)* 6,845 work-related non-fatal injuries to members of the public(4,202 last year)* 27,932 work-related non-fatal injuries to employees (30,882 lastyear).

1

29

300 1

100

500

Heinrich (1931)

Bird (1966)

disabling(major lost-time injury)

minor injury

no injuryaccident disabling injury

minor injury

property damageaccident



The report states that the total time spent on health and safety bylocal authority inspectors has gone down, although higher riskworkplaces are being targeted and the rate of visits per inspector isbeing maintained.

The report also identifies an increase in the level of fines for healthand safety offences. In the year 1999/2000, the average fine perconviction was 4,098, which is an increase of 84% from last year.

In order to help local authorities to improve standards of health andsafety in the sectors that they enforce, the Health and Safety Com-mission (HSC) is planning to help HELA in drawing up an indicatoragainst which local authorities can measure their enforcement andpromotional activity.

Copies of HELA Annual Report 2000 and HELA National Pictureare available free from:

HSE Books, PO Box 1999, Sudbury, Suffolk CO10 2WAtelephone: 01787 881165 website: www.hsebooks.co.uk

Croner Health and Safety Briefing 198, 12 September 2000

Whichever model you favour (and there are plenty of variationson this iceberg / pyramid / triangle theme), the same conclusionsfollow ...... if, through appropriate management of risk, you reduce the no-injury accidents / the property damage accidents (ie the base ofthe iceberg), you will reduce the numbers of the more seriousaccidents occurring higher up.On first reading you may think that the previous sentence is notvery ambitious in its aims - shouldnt the aim be total safety, noaccidents ever; our answer is that in life it is more sensible todevelop a practical approach that works rather than aim for anideal system that doesnt.In section 3 and 4 of this book, we will look further at variousaccident causation theories.



3 Domino theory (single-causal)We will look at two so called single-causal models, that ofHeinrich (section 3.1) and that of Bird and Loftus (section 3.2).

3.1 Heinrichs domino theoryAccording to Heinrich, a preventable accident is one of fivefactors in a sequence that results in an injury. The injury isinvariably caused by an accident and the accident in turn isalways the result of the factor that immediately preceded it.This approach leads to the row of dominoes model of accidentcausation: if you knock over the first domino it knocks the secondand so on. This knock-on effect is easy to imagine andoffers a simple answer to accident causation, namelythat if we remove one of the five dominoes, thenthe sequence is broken and the injury cannotoccur. The following shows the dominosequence:

Heinric

hs dom

inos

Ancestry and social environmentCharacter traits can be passed through inheritance and reinforcedby the social environment. Both factors can lead to faults of theperson.Fault of the personCan lead to unsafe acts and allow unsafe conditions to exist andto continue.



Unsafe acts and conditionsHorseplay and reckless behaviour. Working without guards or ininsufficient light.AccidentEvents such as falls, trips, being hit by flying objects etc resultingin injury.InjuryFractures, lacerations, disablement and death resulting directlyfrom accidents.Which domino do you think it best to remove?Heinrich believed that the first two dominoes can only be removedthrough a lengthy period of education which aims at changingattitudes. This may take place alongside the accident preventionprogramme, but will not produce immediate results. Dominoes 4and 5 occur too far along the accident sequence. Therefore, thebest candidate for the accident prevention programme to focusupon is domino 3 - unsafe acts and conditions.

Personal view

I must admit that ever since I first read about Heinrichsmodel, I have felt a sense of irritation; firstly because thelanguage seems so dated with its overtones of accidentsresulting from moral degeneracy on the part of the worker(s).My second concern was that the domino model wasnt verygood anyway: I never felt happy with the idea of stopping theaccident by removing (say) the second domino - surely, it isreasonable to ask, why cant a new domino-tumbling se-quence start with the third domino?

In any case, life is too complicated to be encompassed by fivedominos. Harbouring a suspicion that probably no-one hadactually read Heinrichs original work for many decades, Iwent back to the original and was pleased to find that it wasnot as outdated and objectionable as I had suspected, butnevertheless, I still felt uneasy with the model



Bird and Loftus showed similar concerns regarding Heinrichsemphasis on the fault of the individual and they adapted thedomino sequence to produce what is generally seen to be a moresatisfactory domino model ...

3.2 Bird and Loftus domino modelThe Bird and Loftus domino sequence - shown here -certainly overcomes some of the objections tothe original Heinrich model but it still hasthe problem of over-simplification: inthe real world several, or indeedmany, accident causes mayoccur at the sametime.

Bird and

Loftus

dominos

Lack of management control

Basic causes (personal and job factors)

Immediate causes

Accident

Loss



4 Multiple-causal accident modelsIn an attempt to develop a more sophisticated accident model - inparticular in response to the over-simplification problem which wejust mentioned - Bird and Loftus and other authorities developeda multi-causal model of accident causation.Immediately, to me at least, this multi-causal model feels muchmore satisfactory - it reflects the fact that many factors will beinvolved in the build-up to an accident, you do not have to choosejust one unsafe action or condition domino, rejecting all otherpossibilities, and so on.Another advantage of the multiple-causal model is that you canextend and modify the tree as additional factors come to light.The multiple-causation approach also changes the emphasis fromthe fault of the person, often the victim, to encompass othercauses such as lack of training. The multiple-causation approachresults in a tree diagram rather than the domino sequence. Atypical tree is shown below:

sub-causes

injury damageor near miss

cause a

cause b

cause c

cause d

cause e

cause f

unsafe acts

unsafeconditions

accident

You will see a relationship between this multi-causation treemodel and the single-causation domino model - dominoes 5 and4 are immediately identifiable on the tree model, domino 3 is splitinto two, and so on.This multiple-causation tree model allows us to investigate thecauses of unsafe acts and conditions in a more sophisticatedway.



As we said earlier in this book, the NEBOSH examiners havefrequently commented that: when answering accident causesquestions, few students support their answers with basic accidentcausation theory. Accordingly ...

Q Choose a few accidents of your own experience and see ifyou can present them in accident tree form. We stronglyencourage you to submit your answers to the Chichestercentre for comment.

By way of another example, consider a worker who wasinjured in the eye by a fragment of drill-bit which shatteredwhen drilling into concrete.

eye injury

sub-causes

is this the workersregular task?

was there adequatesupervision and

instruction?

was the worker awareof the availabilty of

eye protection?

is routine equipmentmaintenanceundertaken?

accident, bitsplinters

cause

poor training

was full range of bitsavailable?

was eye protectionmade available?

are the bits inspectedas part of a

maintenanceprogramme?

unsafe act of wrongselection ofequipment

unsafe condition ofpoor/wrong bit andlack of protection

Working backwards through the tree, the unsafe act would bethe selection of an ordinary bit instead of a masonary bit. Theunsafe condition would be the unsuitability of the bit - perhapsit was in poor condition as well; another component of unsafecondition is that no eye protection was being worn.(In a single-causation model, these unsafe acts and conditionswould be combined in domino 3. It has to be admitted thatlumping acts and conditions together in one domino can be



quite handy as it side-steps categorisation problems - is it anact? is it a condition?)Continuing to work backwards through the tree ... amongst thecauses we would include the workers fault in selecting thewrong bit and his failure to wear eye protection. Thus, inmoving a step back, we are now highlighting the responsibilityof the individual employee involved in the accident. In movingbackwards in this way we will also draw back the veils onmanagement involvement.

To emphasise that, with the multiple causation approach, the treecan always be extended as new factors come to light - there is noartificial cutting-off point as with the single-causation theories.Tree analysis can be a great help in developing recommendationsto prevent recurrence of accidents.We have already hinted that the distinction between unsafe actsand unsafe conditions may not always be clear; it might now beappropriate to say a little more on this subject (not that we willclaim to make it any clearer!).

5 Unsafe acts and unsafe conditionsUnsafe acts are often associated with inappropriate attitudes, lackof knowledge or skill and/or physical unsuitability; unsafe actsmay be sub-divided into: active unsafe acts where employees actively engage in

activities such as the removal of guarding passive unsafe acts where the action is one of habit rather

than conscious thought; clearly this may be difficult to tackle -does management dramatise the dangers involved in order toraise awareness or not - we are all aware of the problemsassociated with such an approach

Unsafe conditions can be sub-divided into the following twocategories: unsafe mechanical conditions: machine design, guarding,

ergonomic matching of the machine to the employees, safesystems of work (including permits to work), effective means of



stopping the machinery in the event of an emergency, and soon

unsafe physical conditions which include environmentalfactors such as noise, temperature, build-up of rubbish etc

You will not need telling that if both unsafe acts and unsafeconditions are present, the likelihood of an accident is that muchgreater; an effective way of demonstrating this idea is as follows:

The remainder of this book firstly pulls together ideas to whichyou will have been introduced elsewhere in our study material (weassume that the present book comes late in your study) andsecondly, for completion, we introduce some ideas which arepursued in more detail at Diploma level.

unsafe acts unsafe conditions

accident potential



6 Classification of accidentsThis is a subject which definitely falls into the category of pursuedin more detail at Diploma level but is we feel well worth a mentionin the present context. The prime purpose of classifying acci-dents is of course to ensure that they can thereby be effectivelyrecorded - a subject we have covered elsewhere in our studymaterial (notably syllabus sections 5.3.3 and 6.3.4 and 6.3.5).The International Labour Office system of accident classificationencompasses the following main headings:

machinerytransport equipmentexplosion or firepoisonous, hot or corrosive substanceselectricityfalls of personsstepping on or striking against objectsfalling objectshandling without machineryhand toolsanimalsother causes

ILO system of accident classification

Accidents may also be classified according to: the nature of the act giving rise to the accident the physical or material cause age, sex and experience of the victim time and nature of the accident the part of the body injuredObviously the method(s) selected will be determined by the use towhich the information is to be put and by the circumstancesinvolved.



7 (Pro)active and reactive monitoring ofhealth and safety performanceAlready covered to the depth you require at Certificate level(syllabus sections 4.3.14.3.3), this subject area may also beseen as a spring-board to the Diploma where it, rightly, occupiesa key position in the syllabus.

As an aside, at this point we should mention the HSE publica-tion HSG 65 Successful health and safety management. Aswe have said elsewhere, this is not in our view an easy bookto digest but it is undoubtedly very important - more than anyother HSE document it encompasses their philosophy onhealth and safety management: policy organisation planning measuring performance auditing and reviewing performanceHSG 65 might be said to be the set text at Diploma level andwe suspect that in years to come it will probably be co-optedto assume that role at Certificate level also.

Returning to your Certificate studies, let us remind you of what wecovered in syllabus sections 4.3.14.3.3 concerning proactive andreactive health and safety monitoring.

Proactive monitoring (increasing called active monitoring)Systems should be measured and checked before things gowrong. This is best achieved by regular safety inspections,sampling and so on, involving the workforce by constantlyasking questions and encouraging them to report potentialhazards. (Syllabus section 4.3.2 is largely concerned withproactive monitoring.)Reactive monitoringInformation relating to failures in health and safety (ie acci-dents and near misses) should be collected and analysed - theorganisation learning from its mistakes. (Several syllabus



sections touch on reactive monitoring, including: 5.3.3, 6.3.4,6.3.5 and 4.3.2.)

The information gained from both the proactive and reactivemonitoring systems can be used to highlight areas of the highestpotential risks and enable management to concentrate on controlsystems that are effective.

8 Safe person and safe place strategiesAs always in health and safety, the correct balance needs to bestruck ... laboriously protecting each individual worker at theexpense of providing a satisfactory working environment for allstrikes the wrong balance and runs counter to the legal require-ment to consider all other means of control before resorting topersonal protective equipment.Of course, there are certain categories of worker who cannot beprovided with a safe place of work; take for example ...... a fireman or other emergency worker; every time (s)he goesinto a fire or has to deal with a chemical spillage, (s)he is at risk.In such situations, the only way that the risk can be reduced is toconcentrate on a safe person strategy, taking into account: personal protective equipment information, instruction and training safe behaviour of the individualIn addition of course to these emergency workers, there will betimes when a worker who normally works in what we mightdescribe as a well-organised safe place environment, becomessomeone who needs to be given the safe person treatment - attimes of accidental spillage, clean-up operations, maintenanceand so on.Striking the appropriate safe place / safe person balance indifferent work environments is the responsibility of all who man-age and it has formed the subject of several Certificate questionsover the years. On that point, let us repeat the requirements ofthe syllabus, see over ...



The concepts of safe place (for example: safe workplace, equip-ment, environment); and safe person (personal protective equip-ment, information, instruction, training, safe behaviour)

NEBOSH Certificate syllabus section 6.3.3

Editors note. This syllabus section is such an important subjectarea but we are aware that if we say more we will end up repeat-ing what we have said elsewhere; accordingly we leave you toprovide more cross references to 6.3.3 ...

safe placesafe workplace

equipment

environment

safe personpersonal protective equipment

information, instruction, training

safe behaviour

requirements of section 2 HASAWA

hearing (3.3.16)COSHH (3.3.10)ionising radiation (3.3.12)PPE Regs (3.3.18)



You may think we have left quite a lot of space for the syllabuscross references, but we think that once you get started, you willsoon find that you may need even more space.As always, we encourage you to contact the Chichester centre ifyou wish to discuss these matters further.

9 Five steps to a safe system of workAgain, this section of our book really acts as a reprise of what wehave already covered (and a preview of a more detailed look atthe requirements of HASAWA and the Management Regulations,syllabus section 7).The five steps recommended by the HSE to enable a safe systemof work to be devised and implemented are as listed below. Wewill then discuss them in turn:Step 1 Assess the taskStep 2 Identify the hazardsStep 3 Define safe methodsStep 4 Implement the systemStep 5 Monitor the system

Step 1 Assess the taskAll aspects of the task and the risks which it presents must beassessed. Hazards to health as well as to safety should beconsidered. There are six key words which will prompt thequestions to be asked in the course of this assessment: what is used, for example:

plant and substances potential failures of machinery toxic hazards electrical hazards design limitations risk of inadvertently operating automatic controls



who does what, for example: delegation training foreseeable human errors ability to cope in an emergency

how the tasks are carried out, for example: procedures potential failures in work methods short cuts lack of foresight of infrequent events

why the tasks are done this way, for example: particular problems with the process alternative methods (possibly safer)

where and when the various tasks are carried out, forexample: how they interact with one another how they affect others in the vicinity

Step 2 Identify the hazardsWhen a task has been assessed, its hazards should be clearlyidentified and the risks weighed up. As we said earlier, whereverpossible the aim should be to eliminate the hazards and reducethe risks before you rely upon a safe system of work - if thehazards can be eliminated altogether there is no need for the safesystem of work.

Step 3 Define safe methodsYour safe system of work may be defined orally, or by a simplewritten procedure or in exceptional cases by a formal permit towork scheme: consider the preparation and authorisation needed at the start

of the job ensure clear planning of job sequences



specify safe work methods include means of access and escape, if relevant consider the tasks of dismantling, disposal etc at the end of

the jobInvolve the people who will be doing the work; their practicalknowledge of problems can help avoid unusual risks and preventfalse assumptions being made at this stage.In those special cases where a permit to work system is needed,there should be a properly documented procedure. It is importantthat everyone understands which jobs need a formal permit towork. Permits to work should: define the work to be done say how to make the work area safe indentify any remaining hazards and the precautions to be

taken describe checks to be carried out before normal work can be

resumed name the person responsible for controlling the jobJobs likely to need a permit to work system include: working in confined spaces hot work on plant containing flammable dusts, liquids, gases

or residues of these cutting into pipework containing hazardous substances work on electrical equipment

Step 4 Implement the systemYour safe system of work must be communicated properly,understood by employees and applied correctly. Employeesshould be aware of your commitment to reduce accidents byusing safe systems of work.Ensure that supervisors know that they should implement andmaintain those systems of work and that employees, supervisorsand managers are all trained in the necessary skills and and are



fully aware of potential risks and the precautions they need toadopt.Stress the need to avoid short cuts. It should be part of a systemof work to stop work when faced with an unexpected problem untila safe solution can be found.Step 5 Monitor the systemMonitoring means periodically checking :

that employees continue to find the system workablethat the procedures laid down in the system of work are

being carried out and are effectivethat any changes in circumstances which require altera-

tions to the system of work are taken into account

Causes and prevention of accidents1 Immediate and underlying accident causes 2 Accident triangle / pyramid / iceberg 2.1 Heinrichs and Birds accident pyramids 3 Domino theory (single-causal) 3.1 Heinrichs domino theory 3.2 Bird and Loftus domino model 4 Multiple-causal accident models 5 Unsafe acts and unsafe conditions 6 Classification of accidents 7 (Pro)active and reactive monitoring of h and s performance 8 Safe person and safe place strategies 9 Five steps to a safe system of work

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Cause and Prevention