The 2026 National Electrical Code rewrites Section 110.16. The substantive changes are not just editorial. They redefine what counts as a compliant arc flash marking, what equipment is in scope, and what data has to appear on the label itself.
This article walks through the technical changes between the 2023 and 2026 editions.
For a field-level look at what fails inspection and what equipment requires labels in practice, see NEC 110.16 Arc Flash Label Requirements: What Fails Inspection.
2023 vs. 2026 NEC 110.16 at a Glance
| Feature | 2023 NEC 110.16 | 2026 NEC 110.16 |
|---|---|---|
| Label requirement | Generic warning label acceptable | Specific calculated data required |
| Ampere threshold | 1,000A and above only | No threshold, all qualifying equipment |
| Data points | References “applicable industry practice” | Voltage, arc flash boundary, incident energy, PPE level spelled out in code |
| Label language | ”Arc-Flash Hazard Warning" | "Arc-Flash Hazard Marking” |
| Enforcement | OSHA (reactive) | AHJ / electrical inspectors (proactive) |
2023 NEC Section 110.16
The 2023 edition divided the section into two subsections.
110.16(A): General applied to switchboards, switchgear, enclosed panelboards, industrial control panels, meter socket enclosures, and motor control centers likely to require examination, adjustment, servicing, or maintenance while energized in non-dwelling occupancies. It required only marking “to warn qualified persons of potential electric arc flash hazards.” Generic warning stickers satisfied this.
110.16(B): Service Equipment and Feeder Supplied Equipment required a permanent arc flash label “in accordance with applicable industry practice” on equipment rated 1,000 amperes or more, including the date the label was applied. The “applicable industry practice” language pointed to NFPA 70E, but the NEC did not spell out specific data points.
2026 NEC Section 110.16
The 2026 edition consolidates both subsections into a single section titled “Arc-Flash Hazard Marking” (replacing “Arc-Flash Hazard Warning”). The new section requires a permanent arc flash marking on all equipment in non-dwelling occupancies likely to require examination, adjustment, servicing, or maintenance while energized, containing:
- The nominal system voltage
- The arc flash boundary
- The available incident energy or minimum required level of personal protective equipment
- The date the assessment was completed
NEC 110.16 labeling requirements are no longer satisfied by generic warning labels. They require calculated data tied to the actual electrical system.
Three Key Technical Changes
No more 1,000A threshold
Detailed label requirements now apply to all qualifying equipment regardless of ampere rating. A 200A panelboard is held to the same labeling standard as a 4,000A switchboard. The threshold that historically excluded smaller panelboards from detailed marking is gone.
Specific data points written into the code
Instead of pointing to “applicable industry practice,” the four required items are explicitly enumerated in the code text. AHJs no longer have to reach into NFPA 70E to identify what belongs on a label. The criteria are now unambiguous and inspectable on their face.
Date of assessment, not date of label
Labels must show when the arc flash study was completed, not when the sticker was applied. This ties directly to NFPA 70E’s five-year review requirement and makes study currency immediately visible at inspection. A label dated 2019 is a code-text-level red flag in 2026.
Language Change: “Warning” Becomes “Marking”
The 2023 section title was “Arc-Flash Hazard Warning.” The 2026 section title is “Arc-Flash Hazard Marking.”
The change is not cosmetic. “Warning” implies general hazard communication. “Marking” implies specific, equipment-tied information. The new language aligns the section with how other NEC marking provisions read and reinforces that the label is an engineering artifact, not a generic sticker.
Enforcement Shift Behind the Technical Changes
The 2026 changes do not introduce new arc flash calculations. IEEE 1584-2018 still governs the math, and NFPA 70E has long required the same data on labels.
What changed is that the requirements are now enforceable by local electrical inspectors at routine inspections, not just by OSHA after an incident. The technical specificity in the new section text is what makes that enforcement workable.
For a breakdown of how this enforcement plays out in the field, where inspectors actually flag labels, and what equipment fails inspection most often, see NEC 110.16 Arc Flash Label Requirements: What Fails Inspection.
What This Means in Practice
Accurate labeling under the 2026 edition depends on a current arc flash study with verified fault current data. If that has not been done or has not been updated, the labels will not survive inspection regardless of how recently they were printed.
For pricing context on what the underlying study costs, see How Much Does an Arc Flash Study Cost? A properly scoped arc flash study produces labels that meet the 2026 requirement and hold up at inspection.
Need an arc flash study aligned with the 2026 NEC?
Zech Engineering provides arc flash studies, short-circuit analysis, and protective device coordination with labels meeting or exceeding 2026 NEC 110.16 requirements.