Arc flash labels provide crucial information about the hazards of electrical equipment. Labels let workers know what the type and degree of electrical hazards are present and what personal protective equipment (PPE) must be worn. Label requirements are set forth in the National Fire Protection Association (NFPA) Regulation 70E. There is not a single standardized layout of labels, but all labels must meet the requirements set forth in NFPA 70E.
Elements of an Arc Flash Label.
The header will fall into one of two categories: Warning or Danger. A red Danger label is used when the system voltage is over 600 V or when the incident energy over 40 cal/cm2. An orange “Warning” header is used for systems with a system voltage of less than 600 V or an incident energy under 40 cal/cm2.
Arc Flash Boundary:
This section displays the shortest distance at which the worker may experience second-degree burns or worse, if not protected by flame-resistant PPE.
Incident Energy and Working Distance OR PPE Hazard Category and Arc Rating of Clothing:
NFPA 70E requires at one of these sections, but not both. This is because both ratings reflect different ways of assessing the hazard, and both are calculated in cal/cm2. Having both sections on a label can cause confusion.
Incident Energy and Working Distance
Incident energy refers to the amount of thermal energy present at a working distance from an arc fault. The thermal energy is usually measured in calories per square centimeter (cal/cm2). The working distance refers to how far away the worker’s head and body is from the arc. The incident energy is highest the closer one gets to the arc, which means arc the hazards can be even more dangerous if a worker is closer than the working distance. The most commonly used working distance is 18 inches.
PPE Hazard Category and Arc Rating of Clothing:
Arc Flash PPE ratings are divided into categories (1-4.4), which indicate the minimum criteria equipment must meet to avoid second-degree burns or worse, if inside the boundary area.
This section indicates the approach limit (required distance) to exposed energized components that present a shock hazard. Unqualified persons cannot pass beyond this limit unless they are wearing the proper PPE and are supervised by qualified persons.
This section indicates the distance and approach limit to exposed energized components where there is an increased risk of shock due to electrical over-arc combined with inadvertent movement. Only qualified persons wearing the proper PPE can cross this boundary. An Energized Electrical Work Assessment must be completed before a worker crosses the Restricted Approach Boundary.
System Voltage (or shock risk):
The overall voltage of the system must be clearly indicated in this section.
This section is not required by NFPA 70E, but is often used for organizational and identification purposes, and to prevent mislabeling.