The Left Hand Side of all electrical bowties, consists of the initiating event and corresponding safety measures preventing direct or indirect contact with electricity.
Reliability, Risk and Safety: Theory and Applications – Briš, Guedes Soares & Martorell (eds) © 2010 Taylor & Francis Group, London, ISBN 978-0-415-55509-8
Occupational risk management for electricity hazard O.N. Aneziris, I.A. Papazoglou & M. Konstandinidou NCSR “DEMOKRITOS”, Aghia Paraskevi, Greece
M. Damen RIGO, Amsterdam, The Netherlands
J. Kuiper Consumer Safety Institute, Amsterdam, The Netherlands
L.J. Bellamy WhiteQueen, Amsterdam, The Netherlands
M. Mud RPS Advies BV, Delft, The Netherlands
H. Baksteen Rondas Safety Consultancy, Nieuwegein, The Netherlands
J. Oh Ministry of Social Affairs & Employment, The Hague, The Netherlands
ABSTRACT: A methodology and associated tools for managing occupational risk owing to contact with electricity is presented. The methodology is based on the principles of quantified risk assessment and management. Three logical models representing contact with electricity while working with high voltage cables, electrical tools or while performing electrical work have been developed. These models provide the logical relationship of a contact with high voltage or the formation of an electrical arc and ensuing possible harm consequences with the various working conditions, prevention and mitigation factors. Risk as probability per hour of exposure for three possible consequences has been assessed. A sensitivity analysis has been performed, assessing the relative importance of measures affecting the working conditions and eventually the risk. The most important measure in order to decrease fatality risk in case of work near overhead lines or high voltage cables is the prevention of access to these lines, while the most important measure in order to decrease fatality risk in case of electrical work or work with electrical tools is the use of personal protective equipment. 1
INTRODUCTION
Occupational fatalities and injuries caused by electricity pose a serious public problem and in occupational accidents of the Netherlands. Contact with electricity constitutes 1.5% of the reported 12500 accidents, which have occurred in the Netherlands between 1998 and 2004, while the number of deaths, permanent and recoverable injuries is on the average 30 per year. Several studies have been performed examining the causes of deaths by electrocution, such as those performed in USA from the National Institute of Occupational Safety and Health (NIOSH), (NIOSH 1995, 1998), by Cawley and Homce (2003), by Janicak (2008), by Williamson and Feyer (1998) in Australia and also causes of electrical arc accidents by Makinen and Mustonen (2003) in Finland.
The Dutch government has chosen the quantitative risk approach in order to determine the most important paths of occupational accidents and optimize the risk reduction efforts. It has embarked the Workgroup Occupational Risk Model (WORM) project, as presented by Ale et al. (2008). Major part of the WORM project is the quantification of occupational risk, according to the bowtie methodology developed within the project and presented by Papazoglou & Ale (2007). Data for the development of these models are derived from the GISAI database (GISAI 2005) of the Netherlands Ministry of Work, which incorporates 12500 occupational accidents, which have occurred in the Netherlands between 1998 and 2004. Of all the analyzed occupational accidents, 186 have been classified as accidents caused owing to contact with electricity. In this paper the 186
721
Figure 1. Bowtie for “contact with electricity-high voltage cables.
accidents have been classified into the following categories: a) Contact with electricity- high voltage cables, consisting of 18 accidents that occurred while working near overhead wires, rail tracks or high voltage cables b) Contact with electricity – electrical work, consisting of 146 accidents that occurred while performing electrical work such as working in switching or control units, installation of high voltage etc; c) Contact with electricity- tool, consisting of 39 accidents that occurred while working with electrical hand tools, electrical office appliances, armatures and house hold appliances. From the observed accident cases, scenario-models have been developed, to capture the sequence of events leading to the accident (Bellamy et al. 2007). The scenario-model is the basis for the final logical modelling in the WORM project (Papazoglou 2007). The logical model developed in WORM consists in successive decomposition of the overall accident consequence into simpler and simpler events until a final level of event resolution is achieved. Each level of events is logically interconnected with the more general events of the immediately upper level. The events of the lower level of decomposition form an influence diagram consisting of two parts distinguished by a main event called the Centre Event (CE) and representing the occurrence of an accident (here contact with electricity or an electrical arc). All events to the left of this event represent events aiming at preventing the CE from occurring and the corresponding part of the diagram is called Left Hand Side (LHS). All events to the right of the CE correspond to events aiming at mitigating the consequences of the CE and this part of the model is called Right Hand Side (RHS) (Papazoglou 2007). The logical model provides a way for organising various events from a root cause via the centre event, ending up with a reportable damage to the health of the worker. The use of such a model is twofold. On the one hand it provides the accident sequences, the sequences of events that lead from a fundamental or
root cause to the final consequence. On the other hand, it provides a way for quantifying the risk (Papazoglou 2007). This paper presents the modeling and quantification, overall quantified risk, the specific causes and their prioritization for all three categories of electrical accidents. It is organized as follows.After the introduction of section 1, section 2 presents the logic models for contact with electricity and risk results. Section 3 presents the ranking of the various working conditions and/or safety measures in terms of their contribution to the risk. Finally section 4 offers a summary and the conclusions. 2
LOGICAL MODEL FOR ELECTRICITY HAZARDS
This section presents three Logical (Bowtie) models developed for “Contact with electricity – high voltage cables”, “Contact with electricity- electrical work” and “Contact with electricity – tool”. It is based on electrical accidents which have occurred in the Netherlands but also and on information about safety rules concerning work with electricity published by NIOSH (1995, 2002). 2.1
Left Hand Side of the models (LHS)
The Left Hand Side of all electrical bowties, consists of the initiating event and corresponding safety measures preventing direct or indirect contact with electricity and also the occurrence of an arc. Figure 1 presents the “Contact with electricity – high voltage cable” bowtie. The initiating event represents working near overhead wires, or rail tracks or high voltage cables. Analysis of the basic laws of electrical energy, coupled with the analysis of the 18 accidents, occurred in the Netherlands, determined two ways in which a worker might get either electrocuted or injured owing to an electric arc, while working
722
Figure 2. Bowtie for “contact with electricity-electrical work. Figure 3. Bowtie for “contact with electricity-tools.
near overhead lines: i) The worker touches with his body (directly) energised electric lines, or he contacts energised electric lines indirectly, by contacting an object or tool which has become live. ii) An electric arc occurs near high voltage cables Correspondingly, there are two primary safety functions preventing these failure modes: a) Provision of measures to avoid direct or indirect contact between a person and electrical lines; b) Provision of measures to avoid the occurrence of an arc. The first safety function is served by the primary barrier “Prevention of Direct or Indirect contact with hot lines” (PSB1). The second safety function is served by three primary barriers: PSB2: Prevention of short circuit from exposed parts PSB3: Prevention of short circuit, owing to insulation failure PSB4: Prevention of an arc owing to failure of electrical wiring All four primary barriers PSB1-PSB4 are defined as two-outcome events, where in the first state the prevention measure exists and in the second it has failed. The occurrence of the initiating event combined with the failure of any of the primary barriers PSB1-PSB4 results to the center event, which is the contact with electricity or an electric arc. Figure 2 presents the LHS of the bowtie “Contact with electricity – electrical work. The initiating event represents performing electrical work. As in the previous bowtie, analysis of the basic laws of electrical energy, coupled with the analysis of real accidents, determined two ways in which a person might get either electrocuted or injured owing to an arc and there are five primary safety barriers preventing this contact, as follows: “Prevention of Direct or Indirect contact with hot lines” (PSB1). PSB2: Prevention of short circuit from exposed parts PSB3: Prevention of short circuit, owing to insulation failure
PSB4: Prevention of an arc owing to failure of electrical component PSB5: Prevention of an arc owing to earthing failure of electrical components. Figure 3 presents the Left hand side of the bowtie “Contact with electricity –tool”. The initiating event represents working with electrical tools, such as electrical hand tools, electrical office appliances, armatures and house hold appliances performing electrical work. Analysis of the basic laws of electrical energy, coupled with the analysis of 39 analysed accidents, determined two ways in which a person may contact electricity while working with electrical tools: a) A person touches with his body (directly)energised parts of the tool b) A person contacts the tool, which has become unexpectedly energised Correspondingly, there are two primary safety functions that ought to prevent these failure modes. The first one prevents a person to come into contact with an energised part of the tool, and the second one prevents a tool to become charged unexpectedly. These safety functions are served by the following safety systems: PSB1: Exposed active parts in tools with safe voltage PSB2: Safe voltage system PSB3: Insulation of active parts PSB4: Earthing of tools PSB5: Double Insulation PSB6: Electrical wires of tool. Exposed active parts in tools with safe voltage (PSB1) In case of work with electrical tools, energised parts should be covered, to prevent a person from physical contact with them. This barrier is defined as having two states: PSB1 (+): Exposed active parts do not exist; PSB1 (−): Exposed active parts exist. Success means that proper covering of live parts of tools is performed and therefore there are no active parts. Failure
723
means that proper covering of live parts of tools is not performed and therefore there are active parts. Safe voltage system (PSB2) In case of work with electrical tools, safe voltage systems may be used. These systems provide 50 V to the user, which is considered safe. This barrier is defined as having three states: PSB2 (1): Safe voltage system present functioning; PSB2 (2): Safe voltage system failed; PSB2 (3): Safe voltage system absent. Insulation of active parts (PSB3) Active parts of electric tools should be insulated, to prevent physical contact with them. This barrier is defined as having two: PSB3 (+): Proper; PSB3 (−): Improper. Success means that proper insulation exists. Failure means that insulation is not proper. Earthing of tools (PSB4) Electrical tools should be earthed (or grounded), so that they don’t become energised in case of a fault. This barrier also is defined as having two states: PSB4 (+): Proper; PSB4 (−): Improper. Success means that earthing (grounding) exists and functions successfully. Failure means that earthing (grounding) is improper and will not protect the tool in case of a fault. Double insulation (PSB5) Double insulation of tools provides protection to the tool and the user, so that the tool cannot be charged in case of a fault. This barrier is defined as having two states: PSB5 (+): Proper; PSB5 (−): Improper. Success means that double insulation exists and is proper. Failure means that double insulation is improper and will not protect the tool in case of a fault. Electric wires of tool (PSB6) The condition of an electrical tool affects its safety. This barrier is defined as having two states: PSB6 (+): Proper; PSB6 (−): Improper. Success means that the tool and its wires is in a good condition, while failure means that it is in a substandard condition. Two additional safety measures have been considered in all three bowties, influencing the contact with electricity. These are a) Personal Protective Equipment for prevention from electrocution, such as rubber insulating gloves, insulated footwear and nonconductive equipment for face, neck and chin b) Personal Protective Equipment for prevention from arc such as: flash suits, face protection shields, hand protection gloves and foot protection shoes. and c) procedures, in case of vehicle contact with electrical wires. This last measure, which is applied in cases where vehicles operate near overhead lines, includes safety procedures which should be followed in such working situations, described in more detail by Damen and Aneziris (2008). 2.1.1 Support Safety Barriers A Support Safety Barrier (SSB) contributes to the adequate function of the Primary Safety Barriers and
influence the probability with which the primary safety barrier-states occur. There are several support barriers, affecting the primary barrier “Prevention of Direct or Indirect contact with hot lines (PSB1)” of bowties “Contact with electricity-high voltage cable” and “Contact with electricity-electrical work”, which are the following: a) Cover or Shielding (SSB1) In case somebody works near overhead lines, or performs electrical work, energised lines should be protected with insulated barriers, to prevent physical contact. b) Safe distance to uninsulated active parts (SSB2) This measure models the distance which should be maintained, when working near overhead lines, both from people and from vehicles such as cranes. Safe distance depends on the voltage of the lines and have been suggested by NFPA (2004). c) Prevention of access to active parts (SSB3) This barrier refers to measures, such as locks doors etc, which prevent access to active parts. Improper access prevention of active parts can lead to violation of the safe 2.2 Probability Influencing Entities (PIEs) In several instances the safety barriers of the model are simple enough to link directly to easily understood working conditions and measures as in the barrier “Prevention of access to active parts”, which affects “Prevention of Direct or Indirect contact with hot lines”. Assessing the frequency with which access prevention exists is straightforward. In other instances, however, this is not possible. For example, the support barrier “Safe distance to uninsulated parts” may be analysed into more detailed and more concrete measures that affect its quality. Such specific measures are: i) awareness that safety distance from uninsulated wires should be kept ii) visibilty of wires iii) signs/communication informing to keep safe distance iii) Adequate space for manoeuvring. Such factors have the name of Probability Influencing Entities (PIEs). Each influencing factor (PIE) is assumed to have two possible levels, “Adequate” and Inadequate”. The quality of an influencing factor is then set equal to the frequency with which this factor is at the adequate level in the working places. Then the quality of the barrier is given by a weighted sum of the influencing factor qualities. The weights reflect the relative importance of each factor and are assessed by the analyst on the basis of expert judgement. Currently equal weights have been used. This way the probability of a support barrier to be in one of its possible states is given by the weighted sum of the frequencies of the influencing factors (RIVM 2008). PIEs and their frequencies as well as the failure probability for the barriers they influence for this bowtie are presented in Table 1. Frequencies of PIEs have been assessed through surveys of the working condition in the Dutch working population and reflect the Dutch National Average RIVM (2008).
724
Table 1.
PIES characteristics and frequencies.
Barrier
PIEs
Bowtie “Contact with electricity- wires” Cover or Shielding • Worker not kept away from lines by signals, barriers, safeguards • Safeguards present but insufficient for body parts • Safeguards present but insufficient for vehicles Close to uninsulated active parts • Not awareness of the high voltage • Lines not visible • Signals, barriers not present • Insufficient room for manouvring Access Prevention of active parts • Ignored access prevention PPE protecting from electrocution • Protection from electrocution PPE protecting from arc • Protection from arc Procedures • Procedures in case of vehicles which may become live Bowtie “Contact with electricity- electrical work” Cover or Shielding • Dangerous parts not covered • Insufficient cover • Cover removed Close to uninsulated active parts • Intentional entrance to dangerous zone • Wrong tools or wrong use • Installing or disassembling under tension • Insufficient room for maneuvering Access Prevention of active parts • no procedure to prevent unauthorized persons working on low/high voltage systems • Possible to ignore the access security PPE • Personal protective equipment Procedures • Working alone with high voltage • Procedure of safe conduct unknown Bowtie “Contact with electricity- tools” PPE
2.3
PIE frequency
Barrier failure Prob.
0.3
0.2233
0.15 0.22 0.11 0.14 0.22 0.08 0.06 0.34 0.33 0.59 0.27 0.2 0.22 0.34 0.05 0.21 0.15 0.16 0.26 0.25 0.02 0.36
0.1375
0.23 0.19
0.21 0.19
0.39
Right hand side (RHS)
The right hand side of contact with electricity bowties in combination with the outcome of the centre event determine the consequences of the contact. Four levels of consequences are used: C1: No consequence; C2: Recoverable injury; C3: Permanent injury; C4: Death. Events of the RHS are the voltage of the current passing through the body and the medical attention. More details on these events are presented by Damen and Aneziris (2008). 2.4
Risk quantification
Individual risk of death, permanent injury and recoverable injury per hour have been assessed for all electrical bowties, according to the methodology presented by Aneziris (2008), Papazoglou et al (2008) and are presented in Fig. 4. Quantification of the model given an exposure of 2.1 × 108 hours for bowtie “Contact with electricity–high voltage cable”, 7.96 × 109 hours for bowtie “Contact with electricity –tools” and 1.269 for bowtie “Contact with electricity – electrical work” in the 6 year period 1998–2004, resulted in the following probabilities: “Contact with electricity – high voltage cables” Probability of Contact with electricity: 8.4 × 10−8 /hr
Figure 4. Individual risk per hour for electrical hazards.
Probability of Recoverable Injury: 4.8 × 10−8 /hr Probability of Permanent Injury: 1.8 × 10−8 /hr Probability of Fatality: 1.9 × 10−8 /hr “Contact with electricity – electrical work” Probability of Contact with electricity: 1.16 × 10−7 Probability of Recoverable Injury: 8.0 × 10−8 Probability of Permanent Injury: 2.8 × 10−8 /hr Probability of Fatality: 8.0 × 10−9 /hr “Contact with electricity – tools” Probability of Contact with electricity: 4.9 × 10−9 Probability of Recoverable Injury: 3.2 × 10−9
725
Table 2.
Fatality risk importance measures for each PIE.
Safety barrier Contact with electricity- wires Base case Worker not kept away from lines by signals, barriers, safeguards Safeguards present but insufficient for body parts Safeguards present but insufficient for vehicles Not awareness of the high voltage Lines not visible Signals, barriers not present Insufficient room for manouvring Access Prevention of active parts ignored Protection from electrocution Protection from arc Procedures in case of vehicles which may become live Contact with electricity- tools Base case PPE Contact with electricity- electrical work Base case Dangerous parts not covered Insufficient cover Cover removed Intentional entrance to dangerous zone Wrong tools or wrong use Installing or dissasembling under tension Insufficient room for manouvring no procedure to prevent unauthorised persons working on low/high voltage systems Possible to ignore the access security PPE Working alone with high voltage Procedure of safe conduct unknown
Probability of Permanent Injury: 1.1 × 10−9 /hr Probability of Fatality: 6.3 × 10−10 /hr Contact with electricity-electrical work has the higher risk for recoverable and permanent injury 8.01 × 10−8 /hr and 2.78 × 10−8 /hr respectively, while contact with electricity-high voltage cables has the higher fatality risk 1.91 × 10−8 /hr of exposure. The bowtie contact with electricity- tool has the lowest risk, in all three consequences.
3
IMPORTANCE ANALYSIS
To assess the relative importance of each factor influencing the risk from contact with electricity, two importance measures have been calculated. 1) Risk decrease: This measure gives the relative decrease of risk, with respect to the present state, if the barrier (or PIE) achieves its perfect state with probability equal to unity. 2) Risk increase: This measure gives the relative increase of risk, with respect to the present state, if the barrier (or PIE) achieves its failed state with probability equal to unity.
Risk rate
Risk Decrease
Risk rate
Risk Increase
1.91E-08 1.55E-08
0.438321
1.91E-08 2.75E-08
0.189375
1.73E-08 1.64E-08 1.65E-08 1.57E-08 1.38E-08 1.72E-08 8.53E-09 1.68E-08 1.66E-08 1.64E-08
0.532475 0.488537 1.107692 1.070319 0.970657 1.145065 8.6616 0.22778 0.26541 0.488537
2.93E-08 2.84E-08 4.03E-08 3.95E-08 3.76E-08 4.1E-08 1.84E-07 2.34E-08 2.41E-08 2.84E-08
0.095221 0.13916 0.138077 0.17545 0.275111 0.100704 0.55287 0.11734 0.13072 0.13916
6.28E-10 2.06E-10
1.0511
6.28E-10 1.29E-09
0.67202
7.94E-9 6.32E-09 6.74E-09 6.62E-09 5.40E-09 7.56E-09 6.37E-09 6.82E-09 6.32E-09
2.04E-01 1.51E-01 1.67E-01 3.19E-01 4.73E-02 1.97E-01 1.41E-01 2.04E-01
7.94E-9 5.51E-01 6.04E-01 5.89E-01 6.19E-01 8.91E-01 7.41E-01 7.97E-01 5.51E-01
1.23E-08 1.27E-08 1.26E-08 1.29E-08 1.5E-08 1.38E-08 1.43E-08 1.23E-08
6.74E-09 6.62E-09 5.40E-09 7.56E-09
1.51E-01 1.67E-01 3.19E-01 4.73E-02
6.04E-01 5.89E-01 6.19E-01 8.91E-01
1.27E-08 1.26E-08 1.29E-08 1.5E-08
Risk decrease prioritizes the various elements of the model for the purposes of possible improvements. It is more risk – effective to try to improve first a barrier with higher risk decrease effect than another with lower risk decrease. Risk increase provides a measure of the importance of each element in the model to be maintained at its present level of quality. It is more important to concentrate on the maintenance of a barrier with high risk increase importance than one with a lesser one. The effect each PIE has on the overall risk is presented in Figs 5–8. “Contact with electricity- high voltage cables” The most important measure in order to decrease fatality risk is the prevention of access to active parts. If used 100% of the time work is performed near electrical wires, it will decrease risk by 54%. The most important measure in order to maintain risk is to prevent access to active parts. If this is not done risk increases by 9.66 times. Risk indices for all measures are presented in Figs 5 and 6 “Contact with electricity- electrical work” The most important measure in order to decrease permanent and recoverable injury risk is not to work close to uninsulated active parts. If this measure is used 100% while performing electrical work, risk decreases
726
Figure 8. Fatality risk increase and decrease for contact with electricity- tools, for PPE. Figure 5. Risk increase and risk decrease for contact with electricity-high voltage cables for various safety barriers.
time work is performed with electrical tools, fatality risk will be decreased by 67%. If this is not done risk increases 2 times. Risk indices for the only measure considered in this case, Personal protective equipment, are presented in Fig 8.
4
Figure 6. Risk fatality increase and risk decrease contact with electricity- high voltage cables, for various working conditions (PIEs).
CONCLUSIONS
A general logical model has been presented for quantifying the probability of contact with electricity and the various types of consequences following all fall from height accidents. The model has been used for risk reducing measures prioritization, through the calculation of two risk importance measures: the risk decrease and the risk increase. REFERENCES
Figure 7. Fatality risk increase and decrease for contact with electricity- electrical work, for various working conditions (PIEs).
67% and 70% respectively. The most important measure in order to decrease fatality risk is the use of PPE. The most important measure to maintain recoverable, permanent injury and fatality risk is again not to work close to uninsulated active parts. If this is not done fatality risk increases by 4, 3 and 2 times respectively. Risk indices for all measures are presented in Fig. 7. “Contact with electricity- tools” The only measure considered in this case is the use of Personal protective equipment. If used 100% of the
Ale B.J.M., Baksteen H., Bellamy L.J., Bloemhof A., Goossens L., Hale A.R., Mud M.L., Oh J.I.H., Papazoglou I.A., Post J., and Whiston J.Y.,2008. Quantifying occupational risk: The development of an occupational risk model. Safety Science, Volume 46, Issue 2: 176–185. Aneziris O.N, Papazoglou I.A., Baksteen H., Mud M.L., Ale B.J.M, Bellamy L.J., Hale A.R., Bloemhoff A., Post J., Oh J.I.H., 2008. Quantified risk assessment for fall from height. Safety Science, Volume 46, Issue 2: 198–220. Bellamy L.J., Ale B.J.M., Geyer T.A.W., Goossens L.H.J., Hale A.R., Oh J.I.H., Mud M.L., Bloemhoff A, Papazoglou I.A., Whiston J.Y., 2007. Storybuilder—A tool for the analysis of accident reports, Reliability Engineering and System Safety 92: 735–744 Cawley J.C, Homce G.T., 2003. “Occupational electrical injuries in the United States, 1992–1998, and recommendations for safety research, Journal of Safety Research, 34, 24–248. Damen M., Aneziris, O., 2008 Technical report on the modelling of Bowties 12: Contact with electricity, WORM Metamorphosis Report. GISAI, 2005. Geintegreerd Informatie Systeem Arbeids Inspectie: Integrated Information System of the Labor Inspection in the Netherlands. Janicak A.C , 2008. Occupational fatalities due to electrocutions in the construction industry, Journal of Safety Research 39, 617–621. NIOSH, Electrocution Fatality Investigation Reports, www.cdc.gov/niosh/injury/traumaelface.html
727
NIOSH, 1998. Worker Deaths by Electrocution, DHHS (NIOSH) Publication No 98–131, U.S. Department of Health and Human Services. NIOSH, 1995. Preventing electrocutions of crane operators and crew members working near overhead power lines, NIOSH Alert, DHHS (NIOSH) Publication No 95–108, U.S. Department of Health and Human Services,www.cdc.gov/niosh/crane.html NIOSH (2002) Electrical Safety, Safety and Health for ElectricalTrades student Manual, DHHS (NIOSH) Publication No 2002–132, U.S. Department of Health and Human Services, 2002,www.cdc.gov/niosh/docs/pdfs/02–123.pdf NFPA 70E, 2004. Standard for Electrical Safety in the Workplace, 2004 Edition. Makinen H, Mustonen S., 2003. Features of electric arc accidents and use of protective clothing in Finland, Safety science, 41, 791–800.
Papazoglou I.A., Ale B.J.M., 2007. A logical model for quantification of occupational risk, Reliability Engineering & System Safety 92 (6): 785–803 Papazoglou I.A, L.J. Bellamy, K.C.M. Leidelmeijer, M. Damen, A. Bloemhoff, J. Kuiper, BJ.M. Ale, J.I.H. Oh, 2008, “Quantification of Occupational Risk from Accidents”, PSAM 9. RIVM 2008 WORM Metamorphosis Consortium. The Quantification of Occupational Risk. The development of a risk assessment model and software. RIVM Report 620801001/2007 The Hague. Williamson A, Feyer A.M (1998). The causes of Electrical Fatalities at Work, Journal of Safety Research, Vol. 29, 3,187–196.
728
