Arc Flash Labels
Arc.flash labels are required by NFPA 70e in the United States and CSA Z462 in Canada. NFPA 70e identifies the minimum arc flash warning label requirements that must be field installed at time of installation. It states:
Article 110.16: Flash Protection. Switchboards, panelboards, industrial control panels, meter socket enclosures, and motor control centers in other than dwelling occupancies, which 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.
To improve safety and worker compliance, additional information can be included on the arc flash label including the flash hazard boundary, working distance and required PPE. When additional arc flash labeling is included, it must be assured that the information is understood by everyone required to work on the equipment. Too much information that is unclear to the workers will be ignored and can be as bad, if not worse, than no information at all. It is extremely important the arc flash label is as clear and accurate as possible. While it is obvious that insufficient PPE is dangerous, over-clothing workers can also increase the risk of an arcing fault due to limited mobility and visibility.
Large equipment such as switchgear can often have different levels of incident energy due to feeder and protective device configuration. Multiple arc flash labels can also be placed on a single piece of equipment depending on the access point and proximity to the arc source for a given activity. However, it is good practice to provide a single arc flash label for the largest incident energy available. Workers should not enter the flash protection boundary to work on live parts unless they are wearing the proper PPE for the level of hazard that could occur. The specific flash protection boundary, working distance, and incident energy values should be readily accessible to all workers, either identified by an equipment mounted label, or otherwise documented and available for reference or review.
The limited, restricted and prohibited approach boundaries stated on an electrical safety warning arc flash label.
Flash Protection Boundary
This boundary number on the arc flash lable dictates the nearest anyone may approach without the use of PPE. In order to determine the flash protection boundary, you need to know the available short circuit current, predicted fault duration and the voltage.
Limited Shock Approach Boundary
The shock approach boundary number on an electrical safety label may only be crossed by an "unqualified" person when they are accompanied by a "qualified" person.
Personal Protective Equipment (PPE) level is dependent on the incident energy at every point a person may perform work on energized electrical equipment. An electrical engineer or other qualified person should first perform the calculations that determine incident energy. Appropriate PPE should cover all parts of the body of the worker that may be exposed to an explosion. This could include shoes, gloves, flame resistant clothing, safety glasses, etc.