The Dangers and Causes of Arc Flash. What is it?

Comply with new regulations, increase safety and save costs with proper identification.

Employees within the workplace are exposed to multiple hazards when working near electrical equipment. In addition to shock, works may be seriously injured, sometimes fatally from arc flash even if they don’t come into direct contact with an energized conductor.

What are you going to do to protect your employees from arc flash hazards? In this post we will discuss three main subjects:

  1. What is Arc Flash
  2. Arc Flash Regulations
  3. Labeling Requirements

We will also share with you additional tools for compliance and various labeling solutions Brady offers.

What is Arc Flash?


Arc Flash is a short circuit through air that flashes over from one exposed live conductor to another conductor, or to the ground.

Arc flash incidents are common and costly, and the frequency of reported accidents is increasing. This is why arc flash has become a very hot topic within OSHA and the safety industry overall.

What Causes Arc Flash?

Arc flashes can be caused in a variety of ways:

  • Just coming close to a high-amp source with a conductive object can cause the electricity to flash over
  • Dropping a tool or otherwise creating a spark can ignite an arc flash
  • equipment failure due to use of substandard parts, improper installation, or even normal wear and tear
  • Breaks or gaps in insulation
  • Dust, corrosion, or other impurities on the surface of the conductor

How Common is Arc Flash?

  • In the past, if someone suffered burns in an electrical accident, people thought the burns were caused by the electrical shock passing through the body. Electrical shocks can cause burns, but what research has shown is that most burns from electrical accidents actually come from arc flash.
  • The majority of hospital admissions due to electrical accidents are from arc flash burns, not from electrical shocks (Taken from NFPA 70E-2004 standard). Of the approximately 350 persons killed in the workplace by electricity last year, roughly 50% were related to arc flash.
  • A report compiled by Capelli-Schellpfeffer, Inc. estimates that five to ten arc flash explosions happen in the USA every day, resulting in 1 to 2 deaths per day.
  • That figure only takes into account incidents where victims were sent to special burn centers. The number does not include the cases sent to regular hospitals or clinics, nor unreported cases or near misses.

What Kind of Injuries Can Arc Flash Cause?

What is the impact of these accidents and what types of injuries can they cause? Injuries from arc flash accidents tend to be very severe and result from two types of hazards: Arc Flash and Arc Blast.

Arc Flash: Electric arcs produce intense heat, and can heat the air to temperatures as high as 35,000 degrees Fahrenheit. This is four times the surface temperature of the sun. Fatal burns can occur when the victim is several feet from the arc. Serious burns are not uncommon even at a distance of 10 feet. Arc flash can cause the following injuries:

  • Skin burns by direct heat exposure
  • Metal is vaporized at this temperature. Droplets of molten metal can be propelled over great distances, causing serious burns or igniting clothing
  • High intensity flash can also cause damage to eyesight

Arc Blast: A high energy arcing fault can produce a considerable pressure wave and sound blast. The intense heat from arc causes the sudden expansion of air, resulting in a blast. A 10,000 A arc at 480 volts is equivalent to 800 MW or approximately 8 sticks of dynamite. Pressure on the chest can be as high as 2000 lbs/sq ft, causing lung collapse. In some cases, the pressure wave has sufficient energy to snap the heads of 3/8-inch steel bolts and to knock over construction walls. Moreover, it can send metal parts flying at speeds over 700 miles per hour. Arc Blast can cause the following injuries:

  • Loss of memory or brain function from concussion
  • Hearing loss from ruptured eardrums (Sound associated with blast can exceed 160 dB. Sound of jet engine: only 145 dB)
  • Shrapnel wounds from metal parts
  • Other physical injuries from being blown off ladders, into walls, ect.

What are the costs of Arc Flash injuries?

  •  Unfortunately, death is a very real possibility with arc flash. Even if the employee survives, he or she may face years of skin grafts and other medical treatment, and may never return to work or enjoy the same standard of life again.
  • Costs to your company can also be significant, with medical treatment running into the millions of dollars. Your company may be tied up in expensive lawsuits with victims and their families. And it’s not just people who get hurt; equipment can be damaged, requiring repair or replacement, and possibly causing the line or even the entire plant to shut down for a period of time.

Your Opportunity to Reduce the Risk

With the rising frequency of reported arc flash accidents and the potential for serious injury or death, arc flash deserves the concern it is generating from within OSHA and the safety industry. To increase safety and ensure compliance throughout your workplace, it is critical to learn and identify arc flash hazards in your facilities, train employees in safe work practices, and use labels and other awareness aids to keep the message in the forefront and reinforce the desired behavior.

Brady can help you achieve these goals in a variety of ways with the wide selection of labels, label printing solutions, and training/awareness tools.

Arc Flash Regulations

New Regulations, NEC Labeling Requirement

OSHA is now citing and fining employers for failure to protect employees from the dangers of arc flash. For guidelines on best practices for protecting employees, OSHA refers employers to the NFPA 70E standard, “Standard for Electrical Safety in the Workplace“.

NFPA 70E instructs employers to conduct an arc flash analysis to determine the amount of thermal energy that could be generated in an arc flash incident. The information is then used to define a flash protection boundary around the potential source, and to determine the level of flame-resistant apparel and other personal protection equipment required when employees cross the boundary while they work on or near exposed live parts.

In addition, the National Electric Code (known as NFPA 70, which is different than the NFPA 70E) added the requirement in 2002 mandating that potential arc flash hazards be labeled to warn of the hazard. The requirement, covered under article 110.16, was updated and expanded in the 2005 version of the NEC.

Labeling Requirements

What needs to be labeled, by whom?

The NEC states that any of the following types of electrical equipment located in manufacturing and commercial establishments (other than dwelling occupancies) must be field marked with a warning label if subject to examination, adjustment, service or maintenance while energized:

  • Switchboards
  • Panelboards
  • Industrial Control Panels
  • Meter Socket Enclosures
  • Motor Control Centers

The labeling requirement is the responsibility of the employer, not the manufacturer or installer of the equipment.
Since the provision took effect in 2002, equipment installed before then technically does not need to be labeled. However, labeling does need to be applied if the equipment is ever modified or upgraded in any way. At least one OSHA representative has stated that he considers changing a fuse or breaker to be a modification that would require labeling. More importantly, from a safety standpoint, the hazard is the same regardless of when the equipment was installed. Consequently, most employers are simply labeling all the appropriate equipment, regardless of when it was installed.
Many employers are also labeling bus ducts and other electrical equipment not specifically called out in 110.16. Again, the logic is the same. If live electrical work may be performed on these systems, the risk of accident and injury exists. Clearly, it is better to properly warn workers of the hazard.
The NEC requirement states that the marking must be located so that it’s clearly visible to qualified persons before they begin work. Typically, the label is placed outside the panel or enclosure door. In some cases, however, companies choose to put the label inside the door (e.g. to protect it from harsh environments), but this should only be done if the door must first be opened (allowing the label to be seen) before the panel face or enclosure can be removed. The key point is that the label is easily noticeable by workers before they may be exposed to any potentially dangerous live parts.

What Needs to Appear on the Label?

The current NEC requirement states only that the label must warn qualified persons of the potential arc flash hazard.

A fine print, information-only note in the NEC requirements refers the reader to ANSIZ535.4-1998, Product Safety Signs and Labels, for guidelines on the design of warning labels. Thus, it is recommended that the header, message, and pictogram, if used, be formatted according to the ANSI standard.

The NEC does not specify whether to use a Danger or Warning header, leaving this up to the employer. Some companies use Warning, some Danger. Some use Danger when the voltage is over 600v or when the incident energy is over 40 cals/cm², and the Warning when it is under that threshold. This should be decided by the employer and used consistently throughout the plant.

In addition to warning of an arc flash hazard, most arc flash labels at least instruct employees to wear the proper personal protection equipment. Many also take the opportunity to warn of electrical shock. The 2″ x 4″ Brady label shown below meets all the NEC requirements and is available in 10 packs or economical 100-label rolls.
Some companies prefer to use additional information identifying when the hazard is present and the potential magnitude of the risk to the employee.

Although not required, they may also choose to include a symbol or pictogram. There are no standards for how an arc flash pictogram should appear. The examples below show the pictogram used by Brady on its arc flash labels.


Labels must be able to withstand their usage environment. This means that the print should not fade, and adhesive should be aggressive enough to avoid peeling. The arc flash labels above are printed on a durable polyester base that is over-laminated to protect the text and graphics. The back of the labels also employ an acrylic adhesive, which allows the labels to be securely and permanently affixed to a wide range of surfaces.

PAC can order any labels you need or require.
Contact us at 888-903-0333.

Portable Arc Flash Labeling Solution

Brady TLS 2200 Thermal Transfer Printer
The TLS 2200 is a lightweight portable printer packed with features to make identifying your structured cabling environment a snap. The thermal transfer printer delivers crisp, clear, non-smearing labels every time and its smart cell technology guarantees ease of use. Just drop the labels in and print!
All-in-One Safety Solution
Brady offers an All-in-One Safety solution for Arc Flash Identification that includes a printer, labels, and label design software.

View these and all the Brady Printing Solutions >

or head directly to our Brady Label Printing Section >

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Mel Meadows

Mel Meadows

Mel Meadows is a product specialist with over 13 years of experience. She’s a central source of expertise for thousands of industrial and critical-class products featured on the Production Automation web store. By working directly with manufacturers, Mel deciphers technical documentation and outlines product use in real-world environments. View her profile to learn more about proper techniques, protocol, and product usage in both industrial and cleanroom facilities.
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