Arc-flash warning labels on commercial equipment

What the code requires

110.16(A): In other than dwelling units, equipment likely to be examined, adjusted, serviced or maintained while energized must be marked, in the field or at the factory, to warn qualified persons of arc-flash hazards. Examples include switchboards, switchgear, enclosed panelboards and motor control centers, as well as industrial control panels and meter socket enclosures.

The (A) marking must meet the field-applied label rules in 110.21(B) and be clearly visible to qualified persons before they examine, adjust, service or maintain the equipment.

110.16(B): In other than dwelling units, service equipment and feeder-supplied equipment rated 1000 A or more must also carry a permanent arc-flash label, applied in the field or at the factory. The label must follow applicable industry practice, such as NFPA 70E, show the date it was applied, and meet 110.21(B).

On the job

• A new service or feeder distribution board rated 1000 A or more needs its arc-flash label in place at installation to pass inspection.
• Producing the (B) label takes arc-flash calculations that may fall outside a basic installation contract. Settle in the contract who is responsible for the label.
• The rule is not retroactive for existing gear, but your inspector may require a label when existing equipment is altered.

Exceptions that matter

• Dwelling units are excluded. Both parts of the rule apply only in other than dwelling units.

What changed in 2023

In 2023 the 110.16(B) threshold dropped from 1200 A to 1000 A, feeder-supplied equipment was added, and the fixed list of label contents was replaced by a reference to applicable industry practice such as NFPA 70E.

Related sections

• NEC 110.21(B): Requirements for field-applied warning labels
• NEC 110.24: Available fault current label at commercial services
• NEC 240.87: Arc energy reduction for breakers of 1,200 A and up

Where this comes from

• California HCAI: 2025 Title 24 Code Cycle Update, Part 3 (CEC) handout (Oct 14 2025)
• Schneider Electric: Arc flash equipment marking requirements (Jun 14 2024)
• Electrical Contractor, Arc-Flash Hazard Warning and Labeling: What the 2023 NEC Has to Say (Dec 15 2022)
• e-Hazard: NEC 2023 Revisions Aim to Improve Safety from Arc Flash Hazards (Jun 21 2022)
• Read the official NEC free at NFPA