OSHA Letter of Interpretation: Marking of Electrical Equipment for Arc Flash Hazards

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OSHA Letter of Interpretation: Marking of Electrical Equipment for Arc Flash Hazards

In 2006, OSHA responded to questions on several topics. Some of these questions still come up.

The first question and response on marking of electrical equipment for arc flash hazards, are copied below. To read the answers to other questions, concerning FR clothing requirements for electrical installations covered by Subpart S and General Duty Clause violations, read OSHA’s Letter of Interpretation here.


When work must be performed on energized electric equipment that is capable of exposing employees to arc-flash hazards, does OSHA require the marking of the electric equipment to warn qualified persons of potential electric arc-flash hazards — i.e., as required by NFPA 70E-2004?1


OSHA has no specific requirement for such marking. A requirement to mark equipment with flash hazard warnings was not included in the 1981 Subpart S revision. However, paragraph (e) of §1910.303 requires employers to mark electrical equipment with descriptive markings, including the equipment’s voltage, current, wattage, or other ratings as necessary. OSHA believes that this information, along with the training requirements for qualified persons, will provide employees the necessary information to protect themselves from arc-flash hazards.

Additionally, in §1910.335(b), OSHA requires employers to use alerting techniques (safety signs and tags, barricades, and attendants) . . . to warn and protect employees from hazards which could cause injury due to electric shock, burns or failure of electric equipment parts. Although these Subpart S electrical provisions do not specifically require that electric equipment be marked to warn qualified persons of arc-flash hazards, §1910.335(b)(1) requires the use of safety signs, safety symbols, or accident prevention tags to warn employees about electrical hazards (e.g., electric-arc-flash hazards) which may endanger them as required by §1910.145.

1 Section 400.11 of NFPA 70E-2004 states: Switchboards, panelboards, industrial control panels, and motor control centers that are in other than dwelling occupancies and are likely to require examination, adjustment, servicing, or maintenance while energized shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.

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Hugh Hoagland

does research and testing of PPE exposed to electrical arcs and is an arc flash expert. Hugh is a Sr. Consultant at ArcWear and Sr. Partner at e-Hazard. Read more about Hugh.

This Post Has 2 Comments

  1. Avatar
    lee meitzler

    is there a requirement for being arc flash trained to replace a breaker in a low voltage breaker panel.

    1. Ken Sellars
      Ken Sellars

      OSHA expects anyone exposed to an electrical hazard to be trained in accordance with that hazard, as does NFPA 70e. If an employee is to replace a circuit breaker, that employee must be trained in the concepts of creating an electrically safe working condition, proper electrical boundaries, arc flash PPE requirements, proper meter usage, and a host of other concepts. These requirements apply to any voltage source 50 volts or greater, and can even go lower is an arc flash is possible, such as is that case in a significant DC power source. The typical required training must cover shock hazard, arc flash hazard, arc blast hazard, appropriate protection methods from those hazards, as well as hazard recognition and risk reduction techniques. These are all covered in a well-developed electrical safety program and associated training. Let me know if you need more information, as e-Hazard does provide these services.

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