Introduction
Electricalinjuriesareaseriousworkplacehealthand safetyissue.Thisguidancehelpsemployerswhose workersinteractwithliveequipmentorcircuits,and thoseinpowergeneration,transmission,and distributiontoidentify,assess,andmitigatearcflash (alsoknownaselectricarc)hazards.Whilearcflash incidentscanoccurinanysettingwithelectrical equipment,arcflashestypicallyinvolvelargeelectrical panels,motorcontrolcenters,electricalswitchboards, transformers,disconnectfusesandmetal-cladswitch gears.
ResearchbytheFireProtectionResearchFoundation,an affiliateoftheNFPA,determinedthattheprincipalinjury eventsassociatedwithelectricalhazardsareelectric shocks,1 arcflashes,andarcblasts. 2
Specificarcflashstatisticsaredifficulttoquantify,and multiplesourcesprovidedifferinginformation,but theyallpresentalarmingdata.NFPAestimates,inits70E StandardforElectricalSafetyintheWorkplace,thatfiveto tenarcflashexplosionsoccurdailyacrosstheUS. Similarly,theIndustrialSafetyandHygieneNews,states thatuptotenarcflashincidentsoccureveryday, “totalingmorethan3,600disablingelectricalcontact injurieseachyear.”3
Anelectricarcisatypeofelectricalexplosion.The electricarcproducesabrightflash,wheretemperatures canexceed35,000°F(19,400°C),nearlyfourtimesthe temperatureofthesurfaceofthesun.Thisenergy createsanexplosiveblast,orarcblast,thatproduces deafeningsound,supersonicconcussiveforces,and superheatedshrapnel.
Arcflashincidentscanigniteclothing,causestructural fires,andproduceparticlesofmoltenmetal,causing severeorevenfatalburninjuries.Atthesehigh temperatures,mostitemswithin3feet(0.9meters), includingskinandflammableclothing,willburn,melt,or vaporize.Mostarcflashburninjuriesoccurwhenthearc ignitesflammableclothingandnotfromthearcitself.
1. Electricshocksresultfromdirectcontactwithexposedenergizedsourceorpartwheretheelectriccurrentrunsthroughthe bodypartmakingcontact.Electricshockscancauseminorinjurieslikeburnsorseriousissueslikeheartproblemsdepending onthestrengthoftheelectriccurrentandthelengthofexposuretime.
2. “OccupationalInjuriesFromElectricalShockandArcFlashEvents,”RichardB.Campbell&DavidA.Dini,March2015,TheFire ProtectionResearchFoundation.https://efcog.org/wp-content/uploads/Wgs/Safety%20Working%20Group/_Worker%20 Safety%20and%20Health%20Subgroup/Electrical%20Safety%20Task%20Group/Documents/REPORT%20-%20Arc%20Flash %20Occ%20Data%20FINAL.pdf
3. “Inaflash:TakeStepstoprotectworkersfromhazards,”BenitaMehta,IndustrialSafetyandHygieneNews https://www.ishn.com/articles/112500-in-a-flash-take-steps-to-protect-workers-from-hazards
Electrical worker in protective gear.
Beforediscussinghowtoidentifyandmitigatearcflashhazards,twocommonmyths shouldbeaddressed--energizedworkandjustifiedenergizedwork.Manyworkers mistakenlyassumethattheydonotneedarcratedorarcflashrated(AR)personal protectiveequipment(PPE)because theyarenotperformingenergizedwork. Employeesmustunderstandthatworkondeenergizedequipmentisnotthesameas anelectricallysafeworkingcondition(ESWC).4 Deenergizingisjustonesteptowardan ESWC,anditdoesnoteliminateelectricalhazards.5
Additionally,thereisacommonmythamongemployeesthatthejustifiedenergized worktheyareperformingiselectricallysafe.Evenwhenworkisconsidered "justified,"strictsafetymeasuresmustbeimplementedandfollowedtominimizethe risksassociatedwithelectricalhazards.Justifiedenergizedworkreferstospecific situationswhereworkingonornearenergizedelectricalequipmentisdeemed necessaryand“justified”undercertainconditions.Insomeinstances,itmaynotbe feasibleorpracticaltodeenergizetheequipmentformaintenanceorothertasks (suchasinterruptingpowertoahospital)andde-energizationmayintroduceor createadditionalhazards.
Addressing Arc Flash Hazards in a Safety and Health Program
OSHArecommendsthatemployersimplementasafety andhealthprogram.OSHA’spublication, “RecommendedPracticesforSafetyandHealth Programs,”www.osha.gov/safety-management, presentsastep-by-stepapproachtoimplementinga safetyandhealthprogram,builtaroundsevencore elementsthatmakeupasuccessfulprogram:
W Management Leadership
W Worker Participation
W Hazard Identification and Assessment
W Hazard Prevention and Control
W Education and Training
W Program Evaluation and Improvement
W Communication and Coordination for Host Employers, Contractors, and Staffing Agencies
Thisguideshowshowmanagementsystemscanbe usedtoprotectworkersfromarcflashhazardswitha focusonworkerparticipation,hazardidentification andassessment,andhazardpreventionandcontrol
4. NFPA70EdefinesanESWCasastateinwhichanelectricalconductororcircuitparthasbeendisconnectedfromenergized parts,locked-outortagged-outinaccordancewithestablishedstandards(suchas29CFR1910.147),andtestedtoverifythe absenceofvoltage.
5. AccordingtoOSHA’s29CFR1910.333(b)(1)standard,conductorsandpartsofelectricequipmentthathavebeen deenergizedbuthavenotbeenproperlylockedoutortaggedoutmustbeconsideredenergizedparts.
Worker Participation
To be effective, any safety and health program needs the meaningful participation of workers and their representatives. Workers have much to gain from a successful program, and the most to lose if the program
Worker Participation and Arc Flash Safety
Encourage Workers to Participate in the Safety and Health Program
Encourage Workers to Report Safety and Health Concerns
Give Workers Access to Safety and Health Information
Involve Workers in All Aspects of the Program
Remove Barriers to Participation
fails. Employers should leverage the firsthand knowledge and experience of their workers who are directly exposed to arc flash risks:
SafetyCulture:Createaculturewhereworkersfeelcomfortablesharingsafety concernsandparticipatinginsafetyprograms.Acknowledgeandprovidepositive feedbackforworkerswhoraiseconcernsaboutarcflashhazards.Managersand supervisorsshouldmaintainanenvironmentthatinvitesworkerstomakesafety andhealthsuggestions.
ReportingHazards:Workershavearighttoraisesafetyconcerns.Establisha systemforworkerstoreportpotentialarcflashhazardswithoutfearofreprisal. Involveworkersinfindingsolutionstoanyarcflashissuesreported.
FeedbackMechanisms:Regularlyreviewandactonworkerfeedbacktoaddress reportedconcerns.Ensureworkersthatreportedinformationwillonlybeusedto improveworkplacesafety.
Access to Procedures and Guidelines: Ensure workers have up-to-date information on arc flash hazards, safety procedures, required personal protective equipment, and emergency plans.
Training and Education: Provide access to training materials and sessions on arc flash hazards.
Collaborate on Procedures: Involve workers in developing and revising safety procedures and procedures for activities involving arc flash hazards. Analyze arc flash hazards in each step of routine and nonroutine jobs, tasks, and processes.
Customize Training: Design training with worker input to cover relevant arc flash risks and protective measures.
Participatory Inspections: Include workers in safety inspections and audits to spot arc flash hazards.
Ensure Inclusivity: Allow all workers to participate, regardless of skill level, education, or language. Implement multilingual resources as needed.
Support and Resources: Provide necessary resources and time for workers to participate effectively in the safety and health program (i.e., safety and health meetings during regular work hours).
HazardIdentificationandAssessment
Existingregulationsrequireassessingtheworkplacefor hazards,includingelectricarcs,butdonotspecifythe componentsoftheassessment.Thehazardassessment shouldinclude:identificationofhazards(bothelectrical andnon-electrical);thelikelihoodofoccurrenceforeach hazard;theseverityofharmifthehazardweretooccur; andhazardmitigationmeasuresthatwillreducethe hazardtoanacceptablerisk.
Toidentifyandassesspotentialhazards,employers–inconsultationwithworkers–shouldreviewexisting informationaboutworkplacehazardsandperiodically conductaninspectiontofindadditionalhazards. Hazardsthatmayleadtoarcflashesinclude:
W Faulty or malfunctioning electrical equipment,
W Inadequate installation or maintenance practices,
W Operating equipment beyond its rated capacity,
W Unauthorized modifications or alterations to electrical equipment,
W Lack of proper warning systems, such as warning signs and labels,
W Assuming low voltage equipment, 240V and under, cannot produce arcs, and
W Inadequate or insufficient PPE.
Additionally, the likelihood of an arc flash incident increases when exposed energized electrical conductors or circuit parts are subject to various factors:
W Unintentional tool contact with conductive surfaces,
W Inadequate training on safety practices,
W Use of improper equipment or tools,
W Corrosion of conductive contacts,
W Worn or damaged insulation,
W Loose contacts,
W Weather conditions, and
W Impurities like dust or moisture on the insulating material.
Ultimately,arcflashesarelesslikelytooccurwhen equipmentisproperlymaintained.Havingrecognizedthe potentialhazardsrelatedtoarcflashes,employersand workersshouldassesstheirlikelihoodandseverity.
Existingregulationsrequirethatemployersintheelectric powerutilityindustrymakeanestimateofthe“incident heatenergy”availableattheenergizedelectrical conductororequipment(29CFR1910.269(l)(8)(ii)and 29CFR1926.960(g)(2)),oftenreferredtoasan“arcflash riskassessment.”6 Incidentenergyistheamountofheat energy,measuredincaloriespersquarecentimeter(cal/ cm²),thataworkermaybeexposedtoduringanarc flash.Thisenergycancauseburnsorotherinjuriesto aworkernearby.Theestimateofincidentenergywill determine:
W The distance between the arc flash boundary and the energized source,
W The incident energy at the working distance, and
W The level of PPE required to safely perform any permitted energized electrical work.
Engineer wearing an arc flash protection suit while performing an inspection.
6. Conductinganarcflashstudyishighlyrecommendedforallemployerswhoseworkersmaybeexposedtoelectricalhazards, not just utility workers.
Limited&RestrictedApproachBoundaryvs.Arc FlashBoundary
NFPA70Erecommendsthatthecloseraworkergetsto theelectricalhazardthemoretrainingandprotection theyshouldhave.Thelimitedandrestricted boundariesareforprotectingagainstelectricshock,not againstarcflashes:
W Restrictedapproachboundary:Insidethis boundaryisthehighestlikelihoodofelectricshock. Undernocircumstanceshouldanunqualifiedworker everbepermittedtocrosstherestrictedboundary. Qualifiedworkersshouldneverenterortake conductiveobjectswithintherestrictedapproach boundaryunlesstheyareusingappropriatePPE, andtheconductiveobjectisinsulated.
W Limitedapproachboundary:Insidethisboundary anelectricshockhazardexists.Whereveritis necessaryforanunqualifiedworkertocrossthe limitedapproachboundary,theunqualifiedworker shouldbesupervisedbyaqualifiedworker(see29 CFR1910.399or1926.968)andaccompaniedwhile insidethelimitedapproachboundary.However,itis importanttonotethatifthearcflashboundaryis withinoroutsidethelimitedapproachboundary, therulesforthearcflashboundaryhavepriority.
However,thearcflashboundaryisspecifictoarcflash hazards,notelectricshock.Additionally,unlikethe electricshockboundaries,thearcflashboundarydoes notfollowasetrelationship.Specifically,therestricted approachboundaryisalwaysinsidethelimited approachboundary.Thearcflashboundary,however, maybeinsideoroutsideofeitherthelimitedor restrictedboundary:
W Arcflashboundary:Atthisboundaryaworker withoutappropriatePPEcouldreceivesecond degreeburnsfromanarcflash.7 Similartothe restrictedboundary,undernocircumstanceshould anunqualifiedworkereverbepermittedtocrossthe arcflashboundary.
Figure1.TheLimitedandRestrictedApproach Boundaries.TheRestrictedApproachBoundaryisALWAYS insidetheLimitedApproachBoundary.
Theseboundariesserveastheminimum allowablesafelimitforaworker,includingany conductivetools/equipment,toapproachan energizedconductororcircuitpart.Insome instances,thearcflashboundaryislargerthan thelimitedapproachboundary(seeFigure2). Thisoccurswhenthereisalargeamountof incidentenergythatmaybereleasedbyanarc flash.Ifemployersonlyrelyonthelimited approachboundary,theymayplaceworkers withinthearcflashboundaryandcould exposethemtoarcflashhazards.Whenever thereisalikelihoodofarcflashincident, employersshoulddetermineanduseboththe arcflashboundaryandthelimited/restricted approachboundariestoensureworkersafety. Employersmustensurecompliancewith minimumapproachdistancessetinapplicable OSHAstandards(29CFR1926.960(c)(1)and29 CFR1910.269(l)(3)).
7. AccordingtoNFPA70Ethearcflashboundaryisthedistancefromanexposedenergizedelectricalconductororcircuitpart wheretheincidentenergyequals1.2cal/cm2 (5.02J/cm2).
Figure2.DifferentArcFlashBoundaries.UnliketheRestrictedand LimitedApproachBoundaries,theArcFlashBoundarydoesnothave asetruleforplacement.ItcouldbeinsideoroutsidetheLimited/ RestrictedApproachBoundaries.
DifficultiesinDeterminingArcFlash IncidentEnergy
MultipleCalculationMethods
Manyorganizationsandconsensusbodieshave developedmethodstocalculatearcflashincidentenergy levels.8 Thesemethodsvaryinapplicability,depending onthesituation,andtheresultsofthemethodsmayvary dramatically.Employerscanmoreaccuratelydetermine thelikelyincidentheatenergytowhichtheirworkers maybeexposedbyusingmultiplemethodsandutilizing themostreasonableandconservativeresults.
WorkingConditionsandEquipmentMaintenance
Ifequipmentisnotproperlymaintainedandkeptingood workingcondition,thecalculationofavailableincident energymaynotbeaccurate.Asaresult,theapproach boundariesmaybeincorrect,leadingtoworkerexposure toarcflashhazards.
HazardPreventionandControl
Thehierarchyofcontrolsrankssafeguardstoprotect workersfromhazards(Figure3).Theyarearranged frommosttoleasteffectiveandinclude:elimination, substitution,engineeringcontrols,administrative controls,andPPE.
Thesefivelevelsofthehierarchycanbeorganized intotwogroups:preventiveandprotectivecontrols. Preventivecontrols–elimination,substitution,and engineeringcontrols–areaimedateliminatingor minimizinghazardsattheirsourcetopreventthem fromoccurringinthefirstplace.Thesecontrolsshould beconsideredfirst,astheyarethemosteffectivein ensuringworkplacesafety.Protectivecontrolsonthe otherhand–administrativecontrolsandPPE–are measuresimplementedtominimizetheimpactofthe hazardorreduceworkers’exposuretothehazard. Protectivecontrolsareutilizedwhenitisnotfeasibleor practicaltoeliminatethehazardcompletely.Employers, inconsultationwiththeirworkers,shouldevaluatetheir safeguardsonaregularbasis,determinetheeffectiveness ofreducingworkers’exposure,andidentifypotential improvements.
The amount of incident energy also depends on how fast the faulty component can be isolated from the source of energy. If the protective device isolating the equipment does not operate as intended (e.g., a breaker not opening as quickly as intended), the arc flash energy will be higher than expected during a fault. Employers must inspect and maintain these protective devices in accordance with 29 CFR 1910.334 to ensure they function as designed.
Additionally, employers should calculate incident energy after each major modification of the electrical system or equipment to account for possible changes in incident energy during an arc flash.
By identifying and assessing arc flash hazards employers can determine appropriate safeguards to protect their employees.
Due to the nature of electrical work, many preventive controls will be difficult or impractical to implement (such as redesigning an existing electrical distribution system). As such, employers often rely on protective controls – administrative controls and PPE – to protect their employees.
The use of administrative controls and PPE require significant and ongoing effort by workers and their supervisors. They are most useful when employers are in the process of implementing other control methods from the hierarchy, when arc flash hazards cannot be reduced to an acceptable level, or to provide an additional layer of protection.
8 ExamplesofcalculationmethodsarefoundinIEEE1584,NFPA70E’sInformativeAnnexD,andcommerciallyavailable software.
Administrative Controls
Administrative controls establish work practices that reduce the duration, frequency, or intensity of exposure to hazards. This may include training, maintenance/ housekeeping, limiting access to hazardous areas or machinery, or adjusting work procedures. Existing regulations require employers to implement administrative controls in certain situations. For example, 29 CFR 1910.335(b)(1) requires the use of safety signs/tags to warn employees of electrical hazards which may endanger them. Additionally, there are training requirements contained in 29 CFR 1910.332 for employees who face a risk of electric shock that is not reduced to a safe level.
Additional examples of administrative controls include:
W Developing and documenting clear, step-bystep procedures for workers exposed to arc flash hazards.
W Barricading the arc flash boundary with caution or danger tape to indicate that work is in progress and unauthorized or unqualified persons must not encroach upon the approach boundaries.
W Providing comprehensive training to personnel on electrical safety and arc flash hazard recognition.
W Ensuring that employees performing the electrical tasks are adequately trained, competent, and certified.
Figure 3. Image by NIOSH {https://www.cdc.gov/ niosh/hierarchy-of-controls/ about/index.html}
W Implementing a permit-to-work system that requires authorization and risk assessment before conducting work on or near energized electrical equipment.
PersonalProtectiveEquipment(PPE)
PPEisworntominimizeexposuretohazards.Examples ofPPEincludeshockandarcrated(AR)garments, includingclothing,footwear,gloves,safetyglasses/face shields,hearingprotection,coats,hardhats,and coveralls.WhenworkersusePPE,employersmust implementaPPEprogramaccordingto29CFR1910.132 or29CFR1926.95&1926.97.Theprogrammustaddress:
W Workplace hazards analysis/assessment
W PPE selection and use
W Replacement of damaged or worn-out PPE
W Employee training
When other control methods are unable to reduce the hazardous exposure to safe levels, employers must provide PPE that is appropriate for the work performed and the body parts covered, and is maintained in a safe, reliable condition and is periodically inspected or tested (29 CFR 1910.335(a)(1)(ii)). This may include:
W While other controls are under development
W When other controls cannot sufficiently reduce the hazardous exposure
W When PPE is the only control option available
EmployersmustnotrelysolelyonPPEalonetocontrol hazardswhenothereffectivecontroloptionsare available.PPEcanbeeffective,butonlywhenworkers useitcorrectlyandconsistently.PPEmightseemtobe lessexpensivethanothercontrols,butrelyingonPPE alonecanbecostlyovertimeifitisnotimplemented correctlyorreliedoninlieuofmoreprotectiveoptions.
PPE:Arc-Rated,RubberInsulated,andFire-Resistant (FR)Clothing/PPE
Asdiscussedabove,mostarcflashburninjuriesoccur whenthearcignitesflammableclothingandnotfrom thearcitself.Wearingflame-resistantorrubber-insulated PPEdoesnotnecessarilyprovidearcflashprotection. SpecificallyratedPPE,knownasarc-ratedpersonal protectiveequipment(ARPPE),isneededtoprotect employeesfromthesehightemperatures.Employerscan stresstheimportanceofwearingtherightPPEbyusing phraseslike,“Don’twearfuel,”toremindworkersthat properARPPEmustalwaysbeused.
Additionally,employersshouldstresstheimportanceof whatworkerswearunderARPPE,sincethearcflash,or themoltenmetalcreated,canunpredictablypenetrate seams,closures,orflapsandigniteflammable undergarments.
PPE:Arc-Ratings
NFPA70EidentifiesfourcategorizationlevelsofARPPE, whereeachnumberrepresentsanincreasedriskof dangerfromarcflashevents.Category1isthelowest levelofarc-ratedPPEandgenerallyrecommendsonlya singlelayerofmaterial.Category2increasesthelevelof protectionbyalsoincreasingtheminimumarcratingof ARclothing,recommendingeyeandhearingprotection; rubber-insulatedgloves;andleathershoes.Categories3 and4furtherboostsprotectionbyrecommendinghard hatsandmultiplelayersofPPE.9
9 ThemostrecentrevisionofASTMF3258(2021)outlinestestingproceduresandperformanceguidelinesforrubberinsulated gloves effective against shock and arc flashes while the most recent revision of ASTM F1959 (2006) outlines testing methods for determining the arc rating of clothing.
Damaged electrical boxes.
Arc Flash PPE
Category
Category 1
Minimum arc
rating of 4 cal/cm2
Category 2
Minimum arc
rating of 8 cal/cm2
Category 3
Minimum arc rating of 25 cal/cm2
Category 4
Minimum arc rating of 40 cal/cm2
(AN) – as needed.
Personal Protective Equipment
Arc-Rated (AR) Clothing Protective Equipment
W AR long-sleeve shirt and pants or AR overalls
W AR face shield or AR flash suit hood
W AR jacket, parka, high-visibility apparel, rainwear, or hard hat liner (AN)
W AR long-sleeve shirt and pants or AR overalls
W AR flash suit hood or AR face shield and AR balaclava
W AR jacket, parka, high-visibility apparel, rainwear, or hard hat liner (AN)
W AR long sleeve shirt
W AR pants
W AR overall
W AR flash suit jacket
W AR flash suit pants
W AR flash suit hood
W AR gloves, or rubber insulating gloves with leather protecters
W AR jacket, parka, high-visibility apparel, rainwear, or hard hat liner (AN)
W AR long sleeve shirt
W AR pants
W AR overall
W AR flash suit jacket
W AR flash suit pants
W AR flash suit hood
W AR gloves, or rubber insulating gloves with leather protecters
W AR jacket, parka, high-visibility apparel, rainwear, or hard hat liner (AN)
W Hard hat
W Safety glasses or safety goggles
W Hearing protection
W Leather footwear (AN)
W Heavy-duty leather gloves, AR gloves, or rubber insulating gloves with leather protectors
W Hard hat
W Safety glasses or safety goggles
W Hearing protection
W Leather footwear (AN)
W Heavy-duty leather gloves, AR gloves, or rubber insulating gloves with leather protectors
W Hard hat
W Safety glasses or safety goggles
W Hearing protection
W Leather footwear
W Hard hat
W Safety glasses or safety goggles
W Hearing protection
W Leather footwear ather
Table 1. NFPA 70E (2021) Arc-Rated PPE Categorization Levels. Credit NFPA
Somejurisdictionshaveoptedtorecognizeanadditional Employers must select appropriate PPE for their workers categoryofarc-ratedPPE.Forexample,theCanadian based on the calculated incident energy, ensuring StandardsAssociationWorkplaceElectricalSafety they are protected from potential arc flash hazards in Standard(CSAZ462)hasdefinedafifthcategoryofarc- accordance with 29 CFR 1910.269(l)(8)(v) and 29 CFR ratedPPE.Category5arc-ratedPPEisratedtohavea 1926.960(g)(5). minimumarcflashprotectionof75cal/cm2 (313.8J/cm2).
Conclusion
Implementingarobustsafetyandhealthprogramcan protectworkersfromarcflashhazards.Safetyandhealth programsfosteraproactiveapproachto“findingand fixing”workplacehazardsbeforetheycauseinjuryor illness.Ratherthanreactingtoanincident,management andworkerscollaboratetoidentifyandsolveissues beforetheyoccur.Byidentifying,assessing,preventing, andcontrollingtherisksassociatedwitharcflash hazards,employerscanprotecttheirworkersfrom incidents.Employersshouldemphasizethedistinction between‘deenergized’and‘lockedout/taggedout,’and highlighttheconsistentuseofARPPE.
Employerswillfindthatimplementingasafetyandhealth programalsobringsotherbenefits.Safetyandhealth programshelpbusinesses:
W Prevent workplace injuries and illnesses,
W Improve compliance with laws and regulations,
W Reduce costs, including significant reductions in workers’ compensation premiums,
W Engage workers,
W Enhance their social responsibility goals, and
W Increase productivity and enhance overall business operations.
Formoreinformationonsafetyandhealthprograms, pleasevisit:www.osha.gov/safety-management/.
Additionally,employersshouldsharethefollowingarc flashhazardsguidesspecificallytailoredtoemployees:
W BeingAwareofArcFlashHazards
W CommonElectricalWorkMyths
W EstablishingBoundariesAroundArcFlash Hazards
Engineer wearing an arc flash protection suit while performing an inspection.
