Section 110.16/Arc Flash Hazard Warning
NEC 110.16 requires arc flash warning labels on electrical equipment likely to require examination, adjustment, servicing, or maintenance while energized.
Electrical equipment such as switchboards, switchgear, panelboards, industrial control panels, meter socket enclosures, and motor control centers that are in other than dwelling units and are likely to require examination, adjustment, servicing, or maintenance while energized must be field-marked to warn qualified persons of potential arc flash hazards. The marking must be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance.
Why this section exists
Arc flash incidents can produce temperatures exceeding 35,000 degrees Fahrenheit and blast pressures that can throw a worker across a room. The warning label requirement ensures that anyone working on energized equipment is aware of the hazard before opening the enclosure. While the NEC requires the warning, the detailed arc flash hazard analysis methodology is covered in IEEE 1584, and the PPE requirements are in NFPA 70E.
What plan reviewers look for
Plan reviewers check for a note on the electrical drawings or in the specifications committing to provide arc flash warning labels on all applicable equipment before energization. Some jurisdictions now require the actual incident energy values (calculated per IEEE 1584) to be shown on the one-line diagram or in a separate arc flash schedule as part of the permit submittal.
Common violations
Related NEC requirements
Section 110.24 requires the available fault current to be documented, which is a critical input to the arc flash calculation. Section 240.87 addresses arc energy reduction methods for equipment rated 1200 amps or more. NFPA 70E provides the workplace safety standard for arc flash PPE selection, and IEEE 1584 provides the calculation methodology for incident energy levels.