An electrical hazard is defined by NFPA 70E as a dangerous condition, such that contact or equipment failure can result in electric shock, arc flash burn, thermal burn, or blast.

A qualified person is one who has demonstrated skills and knowledge related to the construction and operation of electrical equipment and installations, and has received safety training to identify and avoid the hazards involved.

Yes, according to NFPA 70E, “unqualified persons shall be trained in, and be familiar with, any electrical safety-related practices necessary for their safety.” (NFPA 70E, 110.6)

An arc flash risk assessment is the process of a facility that identifies arc flash hazards, estimating the potential severity of injury or damage to health and the likelihood of occurrence of injury or damage to health, and determining if protective measures are required.

Facilities are required to update arc flash risk assessments at a minimum of every 5 years, unless major modifications have taken place – in this case, updates must be made sooner.

110.16 only requires the label state the existence of an arc flash hazard. However, it is suggested that the party responsible for the label include more information on the specific parameters of the hazard including:

• Available short-circuit current
• Flash protection boundary
• Incident energy at 18″ expressed in cal/cm2 PPE required
  Voltage shock hazard
• Limited shock approach boundary
• Restricted shock approach boundary
• Prohibited shock approach boundary

Incident energy is defined in NFPA 70E (2015) as the amount of thermal energy impressed on a surface, a certain distance from the source, generated during an electrical arc event. Incident energy is typically expressed in calories per square centimeter (cal/cm2).

NFPA 70E methods estimate incident energy based on a theoretical maximum value of power dissipated by arcing faults. This is believed to be generally conservative.

In contrast, IEEE 1584 estimates incident energy with empirical equations developed from statistical analysis of measurements taken from numerous laboratory tests.

The flow of current through the air between phase conductors or phase conductors and neutral or ground.

An arcing fault can release tremendous amounts of concentrated radiant energy at the point of the arcing in a small fraction of a second resulting in extremely high temperatures, a tremendous pressure blast, and shrapnel hurling at high velocity (in excess of 700 miles per hour).

An arc occurs when electrical current flows between two or more separated energized conducting surfaces. Some arcs are caused by human error including dropped tools, accidental contact with electrical systems, and improper work procedures.

Another common cause of an arc is insulation failure. The fault current’s magnetic effect causes conductors to separate producing an arc. Build-up of dust, impurities, and corrosion on insulating surfaces can provide a path for current. Sparks produced during racking of breakers, replacement of fuses, and closing into faulted lines can also produce an arc. Birds, bees, and rodents can also cause the snapping of leads at connections.

Exposure to an arc flash frequently results in a variety of serious injuries and in some cases death. Workers have been injured even though they were ten feet or more away from the arc center.

Worker injuries can include damaged hearing, eyesight, and severe burns requiring years of skin grafting and rehabilitation. Additionally, equipment can be destroyed, causing extensive downtime and requiring expensive replacement and repair.

The cost of treatment for the injured worker can exceed $1,000,000 / case. This does not include very significant litigation fees, insurance increases, fines, accident investigation, etc. This also does not include process loss to the employer.

Proper worker safety training at regular intervals, preventive maintenance, and an effective safety program can significantly reduce arc flash exposure. Preventive maintenance should be conducted on a routine basis to ensure safe operation.

Worker injuries can include damaged hearing, eyesight, and severe burns requiring years of skin grafting and rehabilitation. Additionally, equipment can be destroyed, causing extensive downtime and requiring expensive replacement and repair.

The cost of treatment for the injured worker can exceed $1,000,000 / case. This does not include very significant litigation fees, insurance increases, fines, accident investigation, etc. This also does not include process loss to the employer.

In order to select the proper PPE, incident energy must be known at every point where workers may be required to perform work on energized equipment. These calculations need to be performed by a qualified person such as an electrical engineer. All parts of the body that may be exposed to the arc flash need to be covered by the appropriate type and quality of PPE.

Proper PPE can include Flame Resistant clothing, helmet or headgear, face shield, safety glasses, gloves, shoes, etc. depending upon the magnitude of the arc energy.

The shock protection boundary is identified as limited approach boundary and restricted approach boundary shall be applicable where approaching personnel are exposed to energized electrical conductors or circuit parts.

*Informational note: In certain instances, the arc flash boundary might be a greater distance from the energized electrical conductors or circuit parts than the limited approach boundary. The shock protection boundaries and the arc flash boundary are independent of each other. The arc flash boundary shall be the distance at which the incident energy equals 5 J/cm2 (1.2 cal/cm2).

The limited approach boundary defines a boundary around exposed live parts that may not be crossed by unqualified person unless accompanied by qualified persons and informed of the possible hazards.

The restricted approach boundary is the area near the exposed live parts that may be crossed only by qualified persons using appropriate shock prevention techniques and equipment. No qualified person shall approach or take any conductive object closer to exposed energized electrical conductors or circuit parts operating at 50 volts or more than the restricted approach boundary.

OSHA is an enforcer of safety practices in the workplace OSHA 1910.132(d), and 1926.28(a) states that the employer is responsible to assess the hazards in the work place, select, have, and use the correct PPE, and document the assessment.

OSHA considers the NFPA standard a recognized industry practice and the administration’s field inspectors carry with them a copy of the NFPA 70E and use it to enforce safety procedures related to arc flash.

The employer is required to conduct a hazard assessment in accordance with 29CFR1910.132(d)(1). Employers who conduct the hazard / risk assessment, and select and require their employees to use PPE, as stated in the NFPA 70E standard, are deemed in compliance with the Hazard Assessment and Equipment Selection OSHA Standard.

Electrical inspectors across the country are now enforcing the new labeling requirements set forth in the National Electric Code (NEC).