/ Field knowledge · NEC 100 · Sparky Edition
A listing mark is not a blank check.
NEC Article 100: a listing mark is not a blank check. Approved, listed, labeled, and identified answer four different questions.
Educational 2026 NEC Article 100 terminology. Confirm the adopted edition. This is not a product listing. Pairs with IMC 301 listed is not installed.
- Approved — acceptability to the AHJ.
- Listed — inclusion in a published list by an organization acceptable to the AHJ after evaluation for a stated purpose.
- Labeled — the label, symbol, or identifying mark carried by the product.
- Identified — suitability for the specific purpose, function, use, environment, or application the Code requires.
They overlap. They are not synonyms. “Is it listed?” can miss the listing basis, the required mark, environmental suitability, compatibility with the equipment served, and whether field modification changed the evaluated configuration.
Modified enclosure, missing mark
If the original mark is missing, the enclosure has been altered, or the installation differs from the evaluated arrangement, photograph it, name the unknown, and route it to the responsible professional, manufacturer, qualified evaluator, or AHJ. Do not convert an unresolved product question into a generic note.
Source: Sparky listed/labeled · IMC 301: listed is not installed · wet location: dry/damp/wet.
What to send
The nameplate photo (safe access), the intended use/environment, and whether the enclosure was modified.
If the schedule says “listed” and the field unit is cut
Send the photo. Masterbuild will say whether Article 100 even has a mark left — or the listing was for a different environment.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Sparky Edition uses the 2026 NEC as model-code education. Confirm the adopted edition. Field observations do not establish electrical safety; only qualified personnel using required safe-work procedures should access electrical equipment.