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Meeting OSHA and NFPA 70E arc flash safety requirements while balancing prevention and production demands
By Ed Rafter

Uninterruptible uptime, 24 x seven, naught downtime…these are some of the terms that characterize data center concern goals for Information technology clients. Given these demands, facility managers and technicians in the manufacture are skilled at managing the infrastructure that supports these goals, including essential electrical and mechanical systems that are paramount to maintaining the availability of business-disquisitional systems.

Electric accidents such as arc wink occur all too often in facility environments that have loftier-energy use requirements, a multitude of high-voltage electrical systems and components, and frequent maintenance and equipment installation activities. A series of stringent standards with express published exceptions govern work on these systems and associated equipment. The U.Due south. Occupational Safety and Health Administration (OSHA) and National Fire Protection Association (NFPA) Standard 70E prepare safe and operating requirements to forbid arc flash and electrical shock accidents in the workplace. Many other countries have similar regulatory requirements for electrical rubber in the workplace.

When these accidents occur they tin can derail operations and crusade serious damage to workers and equipment. Costs to businesses can include lost work time, reanimation, OSHA investigation, fines, medical costs, litigation, lost business, equipment impairment, and most tragically, loss of life. According to the Workplace Rubber Awareness Quango (WPSAC), the average price of hospitalization for electric accidents is US$750,000, with many exceeding The states$ane,000,000.

In that location are reasonable steps data centre operators can—and must—accept to ensure the safety of personnel, facilities, and equipment. These steps offering a threefold do good: the same measures taken to protect personnel likewise serve to protect infrastructure, and thus protect data center operations.

Beyond all industries, many accidents are caused past basic mistakes, for example, electric workers not beingness properly prepared, working on opened equipment that was not well understood, or magnifying risks through a lack of due diligence. Data center operators, still, are already attuned to the bailiwick and planning it takes to run and maintain loftier-availability environments.

While complying with OSHA and NFPA 70E requirements may seem daunting at first, the maintenance and operating standards in identify at many data centers enable this industry to effectively meet the challenge of adhering to these mandates. The performance and rigor required to maintain 24 10 7 reliability means the gap betwixt current industry practices and the requirements of these regulatory standards is smaller than it might at beginning appear, assuasive data centers to balance safety with the demands of mission critical production environments.

In this article we describe arc flash and electrical safe issues, provide an overview of the essential measures information centers must follow to run across OSHA and NFPA 70E requirements, and hash out how many of the existing operational practices and adherence to Tier Standards already places many data centers well along the road to compliance.

Figure ane. An arc flash explosion demonstration. Source: Open Electric

Understanding ARC Wink

Arc wink is a discharge of electrical energy characterized by an explosion that generates low-cal, noise, shockwave, and oestrus. OSHA defines information technology as "a phenomenon where a flashover of electric electric current leaves its intended path and travels through the air from ane conductor to another, or to ground (run into Effigy 1). The results are often trigger-happy and when a human is in close proximity to the arc flash, serious injury and even death can occur." The resulting radiation and shrapnel can cause astringent peel burns and eye injuries, and pressure waves tin can have enough explosive force to propel people and objects across a room and cause lung and hearing damage. OSHA reports that up to fourscore% of all "qualified" electrical worker injuries and fatalities are not due to shock (electrical electric current passing through the body) only to external burn injuries caused by the intense radiant rut and energy of an arc mistake/arc boom.¹

An arc wink results from an arcing electrical error, which tin can be acquired past grit particles in the air, moisture condensation or corrosion on electrical/mechanical components, material failure, or past human factors such equally improper electric system pattern, faulty installation, negligent maintenance procedures, dropped tools, or accidentally touching a live electrical circuit. In brusque, at that place are numerous opportunities for arc flash to occur in industrial settings, peculiarly those in which there is inconsistency or a lack of adherence to rigorous maintenance, training, and operating procedures.

Variables that affect the power of an arc wink are amperage, voltage, the altitude of the arc gap, closure time, three-phase vs. single-phase circuit, and being in a confined infinite. The ability of an arc at the flash location, the distance a worker is from the arc, and the fourth dimension duration of their exposure to the arc will all bear upon the extent of skin damage. The WPSAC reports that fatal burns tin can occur even at distances greater than ten anxiety (ft) from an arc location, in fact, serious injury and fatalities tin occur up to twenty ft away. The majority of hospital admissions for electrical accidents are due to arc flash burns, with thirty,000 arc incidents and 7,000 people suffering burn injuries per yr, two,000 of those requiring access to burn down centers with severe arc flash burns.²

The severity of an arc wink incident is determined past several factors, including temperature, the available mistake current, and the time for a excursion to break. The total clearing time of the overcurrent protective device during a fault is not necessarily linear, as lower error currents tin sometimes consequence in a breaker or fuse taking longer to clear, thus extending the arc duration and thereby raising the arc wink free energy.

Unlike the bolted fault (in which high current flows through a solid conductive material typically tripping a excursion billow or protective device), an arcing fault uses ionized air every bit a conductor, with current jumping a gap betwixt 2 conductive objects. The crusade of the fault unremarkably burns away during the initial wink, but a highly conductive, intensely hot plasma arc established past the initial arc sustains the issue. Arc flash temperatures tin can easily reach 14,000–16,000°F (7,760–8,870°C) with some projections as high as 35,000°F (nineteen,400°C)—more than than three times hotter than the surface of the sun.

These temperatures can exist reached by an arc fault result in as piffling as a few seconds or fifty-fifty a few cycles. The heat generated by the high current catamenia may melt or vaporize the conductive material and create an arc characterized by a brilliant wink, intense heat, and a fast-moving pressure wave that propels the arcing products. The pressure level of an arc blast [upwards to 2,000 pounds/square foot (9765 kilograms/square meter)] is due to the expansion of the metal as it vaporizes and the heating of the air past the arc. This accounts for the expulsion of molten metallic upwardly to x ft away. Given these extremes of heat and energy, arc flashes oft cause fires, which can quickly spread through a facility.

INDUSTRY STANDARDS AND REGULATIONS
To foreclose these kinds of accidents and injuries, information technology is imperative that data heart operators understand and follow appropriate safety standards for working with electric equipment. Both the NFPA and OSHA have established standards and regulations that help protect workers confronting electric hazards and prevent electrical accidents in the workplace.

OSHA is a federal agency (part of the U.Due south. Section of Labor) that ensures safe and healthy working conditions for Americans by enforcing standards and providing workplace prophylactic training. OSHA 29 CFR Part 1910, Subpart South and OSHA 29 CFR Part 1926, Subpart K include requirements for electrical installation, equipment, condom-related work practices, and maintenance for general manufacture and construction workplaces, including data centers.

NFPA 70E is a set of detailed standards (issued at the request of OSHA and updated periodically) that address electrical safe in the workplace. Information technology covers prophylactic work practices associated with electrical tasks and prophylactic work practices for performing other non-electrical tasks that may expose an employee to electrical hazards. OSHA revised its electric standard to reference NFPA 70E-2000 and continues to recognize NFPA 70E today.

The OSHA standard outlines prevention and control measures for chancy energies including electrical, mechanical, hydraulic, pneumatic, chemical, thermal, and other energy sources.  OSHA requires that facilities:

•   Provide and be able to demonstrate a safe programme with divers responsibilities.

•   Calculate the caste of arc flash hazard.

•   Apply correct personal protective equipment (PPE) for workers.

•   Train workers on the hazards of arc flash.

•   Utilise appropriate tools for rubber working.

•   Provide alarm labels on equipment.

NFPA 70E farther defines "electrically safe work conditions" to mean that equipment is non and cannot exist energized. To ensure these conditions, personnel must place all power sources, interrupt the load and disconnect power, visually verify that a disconnect has opened the circuit, lock out and tag the circuit, test for absence of voltage, and basis all power conductors, if necessary.

LOCKOUT/TAGOUT
Most information center technicians will be familiar with lockout and tagging procedures for disabling machinery or equipment. A single qualified individual should exist responsible for de-energizing 1 ready of conditions (unqualified personnel should never perform lockout/tagout, work on energized equipment, or enter high risk areas). An appropriate lockout or tagout device should be affixed to the de-energized equipment identifying the responsible individual (see Effigy 2).

Figure 2. Equipment lockout/tagout

OVERVIEW: WORKING ON ENERGIZED EQUIPMENT
As the WPSAC states, "the most effective and foolproof way to eliminate the risk of electric daze or arc flash is to simply de-energize the equipment." Nonetheless, both NFPA 70E and OSHA analyze that working "hot" (on alive, energized systems) is allowed within the set safety limits on voltage exposures, work zone purlieus requirements, and other measures to take in these instances. Required safety elements include personnel qualifications, take chances analysis, protective boundaries, and the apply of PPE by workers.

Simply qualified persons should work on electrical conductors or circuit parts that take not been put into an electrically safe work condition. A qualified person is 1 who has received training in and possesses skills and knowledge in the construction and performance of electrical equipment and installations and the hazards involved with this type of piece of work. Knowledge or training should encompass the skill to distinguish exposed live parts from other parts of electric equipment, decide the nominal voltage of exposed alive parts, and summate the necessary clearance distances and the corresponding voltages to which a worker volition be exposed.

An arc flash hazard analysis for whatever work must exist conducted to determine the appropriate arc flash purlieus, the incident free energy at the working altitude, and the necessary protective equipment for the chore. Arc flash is measured in thermal energy units of calories per square centimeter (calories/cm2) and arc flash assay is referred to as the incident free energy of the circuit. Incident free energy is both radiant and convective. Information technology is inversely proportional to the working distance squared and directly proportional to the time duration of the arc and to the available bolted fault electric current. Time has a greater consequence on intensity than the available bolted fault current.

The incident free energy and flash protection boundary are both calculated in an arc flash chance assay. There are ii calculation methods, i outlined in NFPA 70E-2012 Annex D and the other in Institute of Electrical and Electronics Engineers (IEEE) Standard 1584.

In practice, to calculate the arc wink (incident energy) at a location, the amount of fault current and the amount of time it takes for the upstream device to trip must be known. A data center should model the distribution system into a software program such equally SKM Ability System Analysis, calculate the short circuit mistake electric current levels and use the protective device settings feeding switchboards, panelboards, industrial control panels, and motor command centers to determine the incident energy level.

BOUNDARIES
NFPA has defined several protection boundaries: Limited Approach, Restricted, and Prohibited. The intent of NFPA 70E regarding arc wink is to provide guidelines that will limit injury to the onset of second degree burns. Where these boundaries are fatigued for whatever specific job is based on the employee'south level of training, the use of PPE, and the voltage of the energized equipment (run across Figure 3).

Figure three. Protection boundaries. Source: Open Electrical

The closer a worker approaches an exposed, energized conductor or circuit part the greater the run a risk of inadvertent contact and the more severe the injury that an arc wink is probable to cause that person. When an energized usher is exposed, the worker may not approach closer than the wink purlieus without wearing advisable personal protective clothing and PPE.

IEEE defines Wink Protection Boundary as "an approach limit at a distance from alive parts operating at 50 V or more that are un-insulated or exposed inside which a person could receive a second caste fire." NFPA defines approach boundaries and workspaces every bit shown in Figure four. Run across the sidebar Protection Boundary Definitions.

Effigy 4. PPE: typical arc wink accommodate. Source: Open Electrical

Calculating the specific boundaries for whatsoever given slice of machinery, equipment, or electrical component tin be done using a variety of methods, including referencing NFPA tables (easiest to practise but the to the lowest degree accurate) or using established formulas, an arroyo calculator tool (provided by IEEE), or ane of the software packages available for this purpose.

PROTECTIVE EQUIPMENT
NFPA 70E outlines strict standards for the blazon of PPE required for any employees working in areas where electric hazards are present based on the task, the parts of the body that demand protection, and the suitable arc rating to match the potential flash exposure. PPE includes items such every bit a flash adjust, switching glaze, mask, hood, gloves, and leather protectors. Flame -resistant article of clothing underneath the PPE gear is also required.

Subsequently an arc flash take a chance assay has been performed, the right PPE tin can be selected co-ordinate to the equipment'south arc thermal functioning exposure value (ATPV) and the break open threshold energy rating (EBT). Together, these components determine the calculated gamble level that any piece of equipment is capable of protecting a worker from (measured in calories per square centimeter). For example, a difficult hat with an fastened face shield provides adequate protection for Hazard/Hazard Category 2, whereas an arc flash protection hood is needed for a worker exposed to Chance/Risk Category 4.

PPE is the last line of defense in an arc flash incident; it's not intended to prevent all injuries, but to mitigate the impact of a wink, should i occur. In many cases, the use of PPE has saved lives or prevented serious injury.

OTHER Safe MEASURES
Additional safety-related practices for working on energized systems could include conducting a pre-work job briefing, using insulated tools, having a written safety program, and flash adventure labeling (labels should indicate the flash chance boundaries for a piece of equipment, and the PPE needed to work within those boundaries), and completing an Energized Electrical Work Allow. Co-ordinate to NFPA, an Energized Electric Work Permit is required for a chore when live parts over l volts are involved. The permit outlines weather and work practices needed to protect employees from arc flash or contact with live parts, and includes the post-obit information:

•   Circuit, equipment, and location

•   Reason for working while energized

•   Shock and arc flash hazard analysis

•   Prophylactic work practices

•   Approach boundaries

•   Required PPE and tools

•   Admission control

•   Proof of chore conference.

DECIDING WHEN TO Work HOT
NFPA 70E and OSHA require employers to evidence that working in a de-energized state creates more or worse hazards than the risk presented by working on live components or is not practical because of equipment design or operational limitations, for example, when working on circuits that are office of a continuous process that cannot be completely shut downwardly. Other exceptions include situations in which isolating and deactivating system components would create a hazard for people not associated with the work, for example, when working on life-support systems, emergency alarm systems, ventilation equipment for chancy locations, or extinguishing illumination for an area.

In addition, OSHA makes provision for situations in which it would be "infeasible" to shut down equipment, for instance, some maintenance and testing operations tin only be washed on live electric circuits or equipment. The decision to work hot should only be fabricated after careful assay of the determination of what constitutes infeasibility. In recent years, some well publicized OSHA actions and statements have centered on the matter of how to interpret this term.

ELECTRICAL SAFETY MEASURES IN PRACTICE
Many operational and maintenance practices will assistance minimize the potential for arc flash, reduce the incident energy or arcing time, or motion the worker away from the energy source. In fact, many of these practices are consistent with the rigorous operational and maintenance processes and procedures of a mission-critical information eye.

Although the electrical industry is enlightened of the risks of arc flash, according to the National Institute for Occupational Safe and Health, the biggest worksite personnel run a risk is withal electrical daze in all but the construction and utility industries. In his presentation at an IEEE-Industry Applications Society (IAS) workshop, Ken Mastrullo of the NFPA compared OSHA 1910 Subpart S citations versus accidents and fatalities betwixt 1 Oct. 2003, and 30 Sept. 2004. Installations accounted for 80% of the citations, while safety work do issues were cited 20% of the time. All the same, installations accounted for 9% of the accidents, while safe work exercise bug deemed for 91% of all electrical-related accidents. Looking at Mastrullo'southward information, while the bulk of the OSHA citations were for installation problems, the bulk of the injuries were related to work exercise problems.

Can OSHA cite yous as a visitor that does not comply with NFPA 70E? The simple answer is: Yes. If employees are involved in a serious electrical incident, OSHA likely volition present the employer/possessor with several citations. In fact, OSHA assessed more ii,880 fines betwixt 2007–2011 for sites not meeting Regulation 1910.132(d), averaging i.5 fines a day.

On the other paw, an OSHA inspection may actually help uncover issues. A May 2012 report of 800 California companies found that those receiving an inspection saw a decline of 9.4% in injuries. On boilerplate, these companies saved The states$350,000 over the v years following the OSHA inspections,^three an outcome far preferable to being fined for noncompliance or experiencing an electrical accident. Beyond the matter of fines, however, any organization that wishes to effectively avoid putting its personnel in danger—and endangering infrastructure and operations—should endeavor to follow NFPA 70E guidelines (or their regional equivalent).

REDUCING ARC FLASH HAZARDS IN THE FACILITY
While personnel-oriented safe measures are the most important (and mandated) steps to reduce the risk of arc wink accidents, in that location are numerous equipment and component elements that can exist incorporated into facility systems that also help reduce the take a chance. These include metal-clad switchgear, arc resistant switchgear, current-limiter ability circuit breakers, and electric current-limiting reactors. Setting upward zone selective interlocking of circuit breakers tin can as well be an effective prevention measure.

TIER STANDARDS & DATA Centre PRACTICES ALIGN WITH ARC Error PREVENTION
Data centers are already alee of many industries in conforming to many provisions of OSHA and NFPA 70E. Many electric accidents are acquired by problems such as dust in the environment, improper equipment installation, and human factors. To maintain the performance and reliability demanded past customers, data center operators take adopted a rigorous approach to cleaning, maintenance, installation, training, and other tasks that forestall arc flash. Organizations that subscribe to Tier standards and maintain stringent operational practices are meliorate prepared to have on the challenges of compliance with OSHA and NFPA 70E requirements, in particular the requirements for safely performing piece of work on energized systems, when such work is allowed per the safe standards.

For example, commissioning procedures eliminate the risk of improper installation. Periodically load testing engine generators and UPS systems demonstrates that equipment chapters is available and helps identify out-of-tolerance conditions that are indicative of degrading hardware or scale and alignment bug. Thermographic scanning of equipment, distribution boards, and conduction paths can identify loose or degraded connections earlier they reach a point of critical failure.

Adherence to rigorous processes and procedures helps avert operator fault and are tools used in personnel training and refresher classes. Facility and equipment design and capabilities, maintenance programs, and operating procedures are typically well defined and established in a mission critical data eye, peculiarly those at a Tier III or Tier IV Certification level.

Beyond the Tier Topology, the operational requirements for every infrastructure classification, as defined in the Tier Standard: Operational Sustainability, include the implementation of processes and procedures for all piece of work activities. Completing comprehensive predictive and preventive maintenance increases reliability, which in plough improves availability. Methods of procedure are mostly very detailed and task specific. Maintenance technicians run across stringent qualifications to perform piece of work activities. Preparation is essential, and planning, practise, and preparation are key to managing an effective information heart facility.

This industry focus on rigor and reliability in both systems and operational practices, reinforced by the Tier Standards, will enable data heart teams to chop-chop adopt and attach to the practices required for compliance with OSHA and NFPA 70E. What still remains in question is whether or non a data middle meets the infeasibility test prescribed by these governing bodies in either the equipment design or operational limitations.

Information technology can be argued that some of today'due south data heart operations approach the status of existence "essential" for much of the underlying infrastructure that runs our 24x 7 digitized order. Data centers support the functioning of global financial systems, power grids and utilities, air traffic control operations, communication networks, and the information processing that support vital activities ranging from daily commerce to national security. Each facility must appraise its operations and system capabilities to enable adherence to safe electrical work practices as much as possible without jeopardizing disquisitional mission functions. In many cases, information technology may become a jurisdictional determination equally to the respond for a specific data heart concern requirement.

No measure out will always completely remove the risk of working on live, energized equipment. In instances where working on live systems is necessary and allowed by NFPA 70E rules, the awarding of Uptime Institute Tier Iii and Tier Iv criteria can assist minimize the risks. Tier Iii and 4 both require the design and installation of systems that enable equipment to be fully de-energized to let planned activities such as repair, maintenance, replacement, or upgrade without exposing personnel to the risks of working on energized electrical equipment

CONCLUSION
Over the last several decades, information centers and the information processing power they provide has become a primal necessity in our global, interconnected club. Balancing the need for appropriate electrical
condom measures and compliance with the need to maintain and sustain uninterrupted production capacity in an energy-intensive environment is a challenge. Only information technology is a challenge the data center industry is mayhap improve prepared to meet than many other industry segments. It is credible that those in the information center industry who subscribe to loftier-availability concepts such equally the Tier Standards: Topology and Operational Sustainability are in a position to readily meet the requirements of NFPA 70E and OSHA from an execution perspective.

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SIDEBAR: PROTECTION BOUNDARY DEFINITIONS
The wink protection purlieus is the closest approach allowed by qualified or unqualified persons without the use of PPE. If the flash protection boundary is crossed, PPE must be worn. The boundary is a calculated number based upon several factors such as voltage, available error current, and fourth dimension for the protective device to operate and clear the fault. It is defined as the distance at which the worker is exposed to i.ii cal/cm2 for 0.1 2d.

Express APPROACH Purlieus
The limited approach boundary is the minimum distance from the energized particular where untrained personnel may safely stand. No unqualified (untrained) personnel may approach any closer to the energized item than this purlieus. The boundary is determined by NFPA 70E Table 130.4-(1) (2) (three) and is based on the voltage of the equipment (2012 Edition).

RESTRICTED APPROACH BOUNDARY
The restricted approach boundary is the distance where qualified personnel may not cantankerous without wearing appropriate PPE. In addition, they must accept a written approved programme for the piece of work that they will perform. This boundary is determined from NFPA Tabular array 130.4-(1) (four)  (2012 Edition) and is based on the voltage of the equipment.

PROHIBITED APPROACH BOUNDARY
Only qualified personnel wearing appropriate PPE can cross a prohibited approach boundary. Crossing this boundary is considered the same as contacting the exposed energized part. Therefore, personnel must obtain a take a chance assessment earlier the prohibited boundary is crossed. This boundary is adamant by NFPA 70E Table 130.iv-(1) (5)  (2012 Edition) and is based upon the voltage of the equipment.

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Ed Rafter

Edward P. Rafter has been a consultant to Uptime Institute Professional Services (ComputerSite Engineering) since 1999 and causeless a full time position with Uptime Constitute in 2013 as main of Educational activity and Training. He currently serves as vice president-Engineering. Mr. Rafter is responsible for the daily management and direction of the professional teaching staff to deliver all Uptime Institute training services. This includes managing the activities of the faculty/staff delivering the Accredited Tier Designer (ATD) and Accredited Tier Specialist (ATS) programs, and whatsoever other courses to be adult and delivered past Uptime Institute.

Boosted RESOURCES
To review the consummate NFPA-70E standards as set forth in NFPA 70E: Standard For Electrical Safety In The Workplace, visit world wide web.NFPA.org

For resources to assist with calculating flash protection boundaries, visit:

•   http://world wide web.littelfuse.com/arccalc/calc.html

•   http://www.pnl.gov/contracts/esh-procedures/forms/sp00e230.xls

•   http:www/bussmann.com/arcflash/index.aspx

To determine what PPE is required, the tables in NFPA 70E-2012 provide the simplest methods for determining PPE requirements. They provide instant answers with almost no field data needed. The tables provide limited awarding and are conservative for well-nigh applications (the tables are not intended as a commutation for an arc hazard assay but just as a guide).

A simplified two-category PPE approach is constitute in NFPA 70E-2012, Table H-ii of Addendum H. This tabular array ensures adequate PPE for electric workers within facilities with large and various electrical systems. Other skilful resources include:

•   Controlling Electrical Hazards. OSHA Publication 3076, (2002). 71 pages. Provides a bones overview
of bones electrical prophylactic on the task, including information on how electricity works, how to protect
against electricity, and how OSHA cab assistance.

•   Electrical Safety: Safety and Health for Electrical Trades Educatee Transmission, U.S. Section of Health and
Human Services (DHHS). National Institute for Occupational Safety and Health (NIOSH), Publication
No. 2002-123, (2002, January). This pupil transmission is function of a condom and health curriculum for
secondary and post-secondary electrical trades courses. It is designed to engage the learner in
recognizing, electrical, and controlling hazards associated with electrical work.

•   Electrocutions Fatality Investigation Reports. National Institute for Occupational Prophylactic and Health
(NIOSH) Safety and Health Topic. Provides information regarding hundreds of fatal incidents involving
electrocutions investigated past NIOSH and state investigators.

•   Working Safely with Electricity. OSHA Fact sheet. Provides safety information on working with
generators, ability lines, extension cords, and electrical equipment.

•   Lockout/Tagout OSHA Fact Sheet, (2002).

•   Lockout-Tagout Interactive Training Plan. OSHA. Includes selected references for preparation and
interactive example studies.

•   NIOSH Arc Wink Awareness, NIOSH Publication No. 2007-116D.

ENDNOTES
1.  http://www.arcsafety.com/resources/arc-flash-statistics

2. Common Electrical Hazards in the Workplace including Arc Flash, Workplace Rubber Awareness Council (www.wpsac.org), produced under Grant SH-16615-07-sixty-F-12 from the Occupational Rubber and Health Administration, U.S. Department of Labor.

3. "The Business Case For Safety and Health," U.S. Department of Labor, https://www.osha.gov/dcsp/products/topics/businesscase/

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Source: https://journal.uptimeinstitute.com/arc-flash/

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