An arc flash is a sudden, massive release of energy from a piece of electrical equipment caused by a fault in the system. The fault can be caused by anything from failing insulation to moisture in equipment to a worker accidentally dropping a screwdriver onto exposed live equipment.
As electrical systems become more complex and reliability becomes more of a need than a want, more and more workers are asked to work on equipment while it is energized. An arc flash that occurs while a worker is in proximity can potentially cause severe injury or even death.
Electrical arc-flash events have reportedly generated temperatures of up to 35,000ºF, nearly four times the temperature of the surface of the sun. Beyond heat and resulting fire, an arc flash can create hazards from flying objects, often molten metal, pressure caused by expanding gases, and sound levels that can reach over 140 dB.
If an owner is asking an electrician or maintenance personnel to work on energized equipment, the liability of providing a safe environment for the worker to do so falls on the owner.
The sections below address the main considerations surrounding arc flash safety and compliance:
- Why Arc Flash Hazards Matter
- Where Arc Flash Requirements Are Found
- What Is Required
- Arc Flash Studies, PPE, and Equipment Labeling
- How Often a System Should Be Evaluated
- Safety, Training, and Preventive Maintenance
Why Arc Flash Hazards Matter?
The threat of inadvertent shock, electrocution, and fire from electrical equipment has long been a known hazard in the electrical industry. In the last 20 years, the industry has turned its attention to arc flash events as a major point of emphasis.
Worker and employee awareness has increased, and national code and standard bodies have made significant progress in studying these hazards, how they occur, and how they can be prevented. Compliance requirements have become more comprehensive with each standard release.
The dangers associated with arc flash include severe burns and death. A facility can face significant financial consequences from an arc-flash incident, along with penalties for failure to comply with established requirements.
Historically, one reason arc flash received increased attention was the January 1, 2009 deadline specified by the National Electrical Safety Code (NESC) for employers to assess potential electrical arc exposure:
“Effective January 1, 2009, the employer shall ensure that an assessment is performed to determine the potential exposure to an electrical arc for employees who work on or near energized parts or equipment.”
— NESC, 2007
The best practice for preventing electrical arc flash is to de-energize parts and equipment prior to servicing them. In many instances, this may not be possible or practical due to maintenance or troubleshooting requirements or the operational effects an equipment shutdown can cause for a facility and its occupants, such as medical equipment, production lines, or equipment troubleshooting.
When energized work is necessary, appropriate analysis, procedures, training, and protective measures become especially significant.
Where Are Arc Flash Hazard Requirements Found?
Arc flash hazard requirements are found throughout various codes and standards, most prominently in NFPA 70E – Standard for Electrical Safety in the Workplace and NFPA 70 – National Electrical Code (NEC).
NFPA 70 governs safe and reliable electrical installations, limiting shock and fire hazards and helping make anyone who comes into contact with the electrical system aware of those hazards.
NFPA 70B – Recommended Practice for Electrical Equipment Maintenance outlines system maintenance and inspection requirements.
NFPA 70E defines worker and employer safety requirements and best practices.
NFPA 70 is an adopted, enforceable code. NFPA 70E is an industry standard rather than a directly enforceable local code.
That distinction does not mean NFPA 70E requirements can simply be ignored.
The Occupational Safety and Health Act is federal law, and OSHA has the authority to issue fines and penalties to employers who violate it. In arc flash incidents, OSHA relies on its general duty clause:
“Each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to employees.”
Since the NEC and NFPA 70E recognize the danger arc flash incidents present to workers, their requirements can play a central role in determining whether employers have provided an appropriate level of electrical safety.
Historically, the National Electrical Safety Code has played a role in these requirements as well. Beginning January 1, 2009, OSHA began enforcing arc-flash requirements associated with facilities that have personnel working on or near live electrical parts.
NFPA 70E requires that employers perform an arc flash hazard analysis on electrical equipment, “conducted for the purpose of injury prevention and determination of safe work practices.” The standard notes that the hazard analysis should identify the Arc Flash Protection Boundary (the distance inside which a person is likely to suffer at least a second degree burn due to the energy released in during an arc flash event) and the appropriate levels of Personal Protective Equipment required.
There are two allowable methods – one is a full Arc Flash Hazard Calculation Study (AFHCS) and the second is via hazard/risk tables found in the standard. It is important to note that a full AFHCS typically requires extensive, sometimes invasive, field survey work to create an accurate model of all components of a facility’s electrical system. This method can be very time consuming, but yields accurate and exact incident energy data and required PPE selection for each piece of electrical equipment. The hazard/risk tables are currently acceptable for determining PPE but provide “typical” results and may leave workers over or under-protected.
Both the NEC and NFPA 70E require employers to provide labels on electrical equipment identifying potential arc flash hazards. NEC doesn’t expound on the content of the label, but NFPA 70E notes that the equipment should be marked with either the required PPE or incident energy (from which required PPE can be determined).
What Is Required?
NFPA 70E requires employers to perform an arc flash hazard analysis on electrical equipment, conducted for the purpose of injury prevention and determining safe work practices.
The analysis should identify:
- The Arc Flash Protection Boundary, or the distance inside which a person is likely to suffer at least a second-degree burn from energy released during an arc flash event.
- The appropriate level of Personal Protective Equipment (PPE).
- The potential incident energy associated with electrical equipment.
- Safe work practices for employees working on or near energized equipment.
According to the NESC 2007 and NFPA 70E 2009 requirements discussed in the original guidance, employers with personnel working on or near energized parts or equipment were expected to:
- Perform an electrical arc flash analysis.
- Install appropriate equipment labeling that includes the incident energy level or required PPE.
- Provide and properly use adequate PPE.
- Implement and follow a safety and training program.
These requirements place arc flash safety within a broader electrical safety program rather than treating the study itself as the end of the process.
Arc Flash Studies, PPE, and Equipment Labeling
There are two allowable methods described for assessing arc flash hazards: a full Arc Flash Hazard Calculation Study (AFHCS) and the use of hazard/risk tables found in the standard.
A full AFHCS typically requires extensive, sometimes invasive, field survey work to create an accurate model of all components of a facility’s electrical system.
This method can be time-consuming but yields detailed incident energy data and required PPE selection for individual pieces of electrical equipment.
The hazard/risk tables provide another method for determining PPE. These tables provide more generalized results and may leave workers over- or under-protected when compared with calculations based on the facility’s specific electrical system.
Equipment labeling forms another part of the requirements.
Both the NEC and NFPA 70E require electrical equipment to be labeled to identify potential arc flash hazards. NEC does not provide the same level of detail regarding label content, but NFPA 70E states that equipment should be marked with either the required PPE or the incident energy from which PPE can be determined.
The 2009 edition of NFPA 70E stated:
“Equipment shall be field marked with a label containing the available incident energy or required level of PPE.”
— NFPA 70E, 2009
Identifying the hazard is only one part of worker protection. The results need to inform equipment labeling, PPE selection, work procedures, and employee training.
How Often Does My System Need to Be Evaluated?
Per NFPA 70E, a revised system evaluation should be performed every five years or when major changes are made to the electrical system.
Major changes include modifications or additions to the distribution system within a facility and changes to the utility distribution network.
Utility companies are not required to notify facilities of changes to their networks that may affect available short-circuit ratings or arc flash calculations. The end user is responsible for making sure facility information remains current.
For facilities that have already completed an arc flash evaluation, this raises two questions:
- Is the study still current?
- Have there been changes to the electrical system or to the utility system serving it since the study was last reviewed?
For facilities that have never completed an evaluation, determining existing hazards and establishing an electrical safety program provide a starting point for addressing worker safety and liability exposure.
Safety, Training, and Preventive Maintenance
Every year, electrical safety accidents rank among the leading causes of workplace fatalities and cause thousands of workers to miss time due to shock and burn injuries.
An arc flash event occurs when electrical current leaves its intended path and travels through the air, causing a sudden release of electrical energy and superheated gases that can severely damage nearby equipment and injure personnel.
Events can be triggered by circumstances as simple as a worker dropping a tool onto exposed live equipment or by dust, condensation, equipment condition, or poor system maintenance.
For employers and facility owners, responsibilities discussed in the standards include:
- Create an electrical safety plan and make sure workers are familiar with the plan, including live work, lockout/tagout (LOTO), PPE, and related procedures.
- Train workers regarding potential electrical hazards.
- Have an arc flash hazard assessment completed by a qualified professional to identify potential energy release, arc flash boundaries, and required protective measures at each point in the system.
- Update the assessment when the electrical distribution system is modified or at least every five years.
- Label electrical equipment in accordance with NEC requirements and NFPA 70E guidance.
- Follow preventive maintenance requirements outlined by NFPA 70B and equipment manufacturers.
The financial impact of fines, production losses, workers’ compensation, healthcare costs, insurance premiums, and potential legal action can be significant. More fundamental than those costs is the responsibility to protect employees from preventable injury or death.
An effective arc flash safety program combines system analysis, labeling, PPE, employee training, safe work procedures, and ongoing electrical equipment maintenance.
Arc flash safety is not a one-time study or labeling exercise. Electrical systems change, utility conditions can change, equipment ages, and maintenance practices affect system performance. Keeping arc flash information current and integrating it into the facility’s broader electrical safety and maintenance program helps personnel understand the hazards present and the protective measures required when work must be performed on or near energized equipment.
Barton Associates has performed power systems studies for facilities ranging from new construction to aging infrastructure and from small standalone retail spaces to higher education and healthcare campus complexes.
For information about coming into compliance, updating an existing study, or performing a new analysis of electrical infrastructure, contact us.