EC-1 Course: NEC Article 100 - Part Two

Definitions of identified, listed and approved terms:


it means acceptable to the inspectional authority [technically, the authority having jurisdiction (AHJ)].


it means generally recognizable as suitable for a specific purpose, environment, or application called out in the NEC requirement. This often comes from product literature generated by manufacturers. Suitability may also be evidenced by listing or labeling, an additional possibility.

Underwriters Laboratories Inc. (UL)

it means that an AHJ (authority having jurisdiction ) has performed exhaustive tests to judge the performance of the product under the conditions contemplated in a specific Code rule, then publish the product in a list stating either that this product meets the specific code rule or has been tested and found suitable for use in a specified manner.


it means that a product to which has been attached a label, symbol or other identifying mark of an organization acceptable to the AHJ and listed this product in their publications.

Sequence for product approval:

  • The manufacturers identify a product to be used for a special application, hence the product is called “identified “product. 
  • The product is sent to a test laboratory to be tested for this application under a specific code rule, if the product passes the tests then this test laboratory list this product in their lists, hence the product is called “listed” product. 
  • Listing of the product is done by attaching a label, symbol or a mark to it, hence the product is called “Labeled” product. 
  • If the product become identified, listed &labeled for a special application, hence the product may be called “approved” product. Why may? The answer is that AHJ may not accept this product even it was identified, listed &labeled, acceptance by AHJ only gives approval sign. 

TUV Rheinland of North America, Inc. (TUV)

From the above sequence, we can extract the following facts:
1- The three Methods of product acceptance which recognized by the NEC are:

  • Identification by product manufacturer.
  • Listing by a test laboratory.
  • Approved by AHJ.
2- A product may be listed by a testing laboratory, but never approved.

3- Identification for a product for a special application is done by manufacturers while listing is done by a test laboratory and approval is done by AHJ (authority having jurisdiction).

4- A mark or a label is an evidence for listing.

Authority Having Jurisdiction (AHJ):

the [AHJ] may be a federal, state, local, or other regional department or individual such as a fire chief; fire marshal; chief of a fire prevention bureau, labor department, or health department; building official; electrical inspector; or others having statutory authority. For insurance purposes, an insurance inspection department, rating bureau, or other insurance company representative may be the [AHJ]. In many circumstances, the property owner or his or her designated agent assumes the role of the [AHJ]; at governmental installations, the commanding officer or department official may be the [AHJ].

National Technical Systems, Inc. (NTS)

But how do you know who all the AHJs are on a project?

The answer: experience. There’s no single source to go to that lists every conceivable AHJ applicable to a particular project type and location. A good way to find out who the AHJs are on a project is to ask: ask the city or county, ask members on the design team (including consultants), ask the owner (this may not be their first project in this location), and ask colleagues who’ve worked on similar projects in the same area. I’m sure there are other sources of information. In either case, eventually (maybe even a couple of years after project completion) you’ll probably know who all the AHJs are on the project, as they’ll make their presence known if something isn’t in compliance, or if the project didn’t go through their agency for review.

Canadian Standards Association (CSA)

Well known test laboratories:

in the next Topic, i will show more definitions from Article 100.

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