NEC 110.16 Explained: The Arc-Flash Warning Section

NEC §110.16 is the National Electrical Code's arc-flash warning requirement — the rule that puts arc-flash labels on electrical equipment. It sits in Chapter 1 (General), which means it applies across the whole code, and its 2026 edition is the version that made detailed labels the default rather than the exception. This page explains what the section does, in plain terms, with the changes dated. Last reviewed: July 18, 2026.

What the section is for

The NEC governs how electrical systems are installed. Section 110.16 exists because installation choices determine what happens years later when someone services the equipment while it is energized. The section requires equipment to carry a warning that is specific enough to act on — not a generic sticker, but the actual hazard data for that equipment: the marker must give a qualified person what they need before the door opens.

Two ideas sit underneath the section:

• The label belongs to the equipment, not to the installer. It is field-applied and stays with the gear; whoever owns the building owns the label's accuracy.
• The label documents an assessment, not a sentiment. The values on it come from an incident-energy analysis or the NFPA 70E tables — "looks dangerous" is not an input.

What the 2026 edition changed

Per EC&M's February 2026 coverage of the code cycle:

The direction is consistent: the code moved from "warn that a hazard exists" to "document the assessed hazard, dated."

Which equipment is covered

The trigger is the same one NFPA 70E uses: equipment likely to require examination, adjustment, servicing, or maintenance while energized. In practice, in non-dwelling buildings: panelboards, switchgear, motor control centers, industrial control panels, disconnects, transformers, and similar service and feeder equipment. Dwelling units sit outside the 2026 expansion.

State adoption decides when this edition becomes law where you are — at research time no state had adopted NEC 2026, Washington targets December 31, 2026, and Maine is moving to amend the section out of its adoption. The adoption tracker keeps the current map. Until your state flips, remember the baseline: NFPA 70E §130.5(H) and OSHA 1910.333 already produce the detailed-label obligation today.

How it interacts with NFPA 70E

The NEC and NFPA 70E are different documents solving adjacent problems: the NEC governs the installation, 70E governs the work. §110.16 tells the equipment what to carry; 70E §130.5(H) tells the employer what the label must contain after a risk assessment — nominal voltage, arc-flash boundary, and incident energy or PPE level. In practice the two produce the same label, which is why our label requirements page treats them as one field set with two citations. The NEC 2026 hub covers the change package as a whole, and the free calculator prints labels that follow both.