Four defined words that decide equipment questions, and the one that is a decision

What the exam asks here

Across the 500 questions in the bank behind this site, 47 turn on one of these four words. Listed appears in 34 of them, identified in 9, approved or approval in 8, and labeled in 4. Ten of the 51 items in the exam-behavior area are built directly on the definitions, and the rest are installation questions where the word in the stem decides the answer.

The distractor that catches people has the manufacturer vouching for its own product. Neither definition describes that. Listed and labeled both turn on an organization that evaluates products and keeps inspecting production, and the difference between the two is where the evidence sits.

The second distractor moves approval into the pair. An option reading listed as approval by the authority is wrong on both halves, because approval is its own defined term and it belongs to a person on the job. Items in this family are open book lookups in Article 100, which makes them among the cheapest marks on the knowledge portion once the four words are straight in your head.

The four words, side by side

Identified does narrower work than listed and broader work than approved. A section calling for a fitting identified for the use is asking for something recognizable as suitable for that specific purpose, and a marking or a listing is the ordinary way suitability gets shown. Candidates who read identified as a demand for a printed phrase on the item rule out fittings that qualify.

Special permission belongs in the same drawer and answers a different question again. Article 100 defines it as the written consent of the authority having jurisdiction, so an option offering written consent where the stem asked about identified equipment is answering a neighboring definition, which is what makes it attractive.

The distinction that decides the answer

Listing is evidence and approval is a decision. That's the sentence that settles most of this family.

An inspector usually leans on a listing while approving something, and the two words keep their separate meanings the whole time. Equipment can carry a listing and still fail to satisfy the authority for the conditions on this particular job, and equipment with no listing can be approved where that authority is satisfied by other evidence. 90.4 is what makes both possible, since it gives the authority having jurisdiction responsibility for approving equipment and materials and for permitting alternatives where the objectives are met.

The examination consequence is direct. Where a stem says approved, the answer names the authority having jurisdiction. Where it says listed, the answer names the evaluating organization and its published list. Where it says labeled, the answer is the mark on the product. Where it says identified, the answer is suitability for the purpose described. Matching the word in the stem to the actor behind it settles items that otherwise take a minute of reasoning about equipment you have never installed, and that minute is a quarter of what the calculations paper allows per item.

What a listing buys the inspection

90.7 explains why the code accepts a listing at all. A qualified organization examined the construction under standard conditions, so factory wiring inside listed equipment stays out of the field inspection, and the work on site covers the field connections and the conditions of use.

Several consequences follow from that one sentence, and each of them turns up as an option somewhere in the bank. Opening listed equipment to verify the factory work answers a question the listing already settled and creates a problem of its own. Altering listed equipment costs it the benefit of that examination. Damage in transit or on site stays yours to find, because the listing speaks to how the item was built and says nothing about what happened to it on the way to you.

The distractors in this family go looking for a threshold. An option having the internal wiring inspected above 100 amperes invites you to turn a factory examination into a field one with an ampere figure, and the code supplies no such figure. Another one has the installer open the equipment, verify the wiring and record it, which sounds diligent and undoes the listing.

Where the 2026 edition puts listing

The 2026 edition ran a uniform section template through the book. An article opens with its scope, carries listing requirements at .2 and reconditioned equipment at .3, and whatever used to sit in those slots moved somewhere else.

That's worth knowing twice over. It tells you where to look when you want to know whether an article requires the equipment it covers to be listed, and it explains why a section number you have used for years now points at something unfamiliar. An older citation for overcurrent protection at 450.3 lands on a heading with its subsections marked reserved, while the rules themselves moved to 450.5. An occupied number costs more than an empty one, because it reads as though you are in the right neighborhood and you get a while into it before noticing.

Several listing requirements in this edition carry delayed effective dates running out to 2032, printed as a sentence at the end of the requirement saying it shall become effective on that date. Those start a requirement on the day named. The book carries expirations too, and those say so in their own words, so the wording decides it and the year tells you nothing. Article numbers that moved are tracked in Informative Annex L.

Instructions and field markings

110.3(B) is the section that turns a manufacturer's installation instructions into something enforceable, because listed equipment is installed according to any instructions included in the listing. That's how an instruction sheet packed with a baseboard heater, ruling out installation below a receptacle outlet, ends up deciding an inspection.

Field applied markings have their own rules and their own distractors. 110.21(B) asks a hazard marking to warn of the specific hazard, to suit the environment it lives in, and to be produced by some means other than a hand and a marker, with a narrow allowance for portions expected to change. Marker fades, and the label exists to be read years later by somebody who was never on the job.

Two other markings turn up often enough to learn. Service equipment at a commercial building carries a field marking giving the available fault current and the date it was figured, updated when a modification could change that current. Equipment applied as a series combination carries a field marking naming the devices that keep the arrangement valid, because the next person to change a breaker has nothing else to go on.

How it shows up in installation items

Once the four words are straight, a family of installation questions collapses into one move: find the word in the stem and name the actor behind it.

• An outlet box that is the sole support of a ceiling paddle fan has to be listed and marked by the manufacturer for that purpose. Fastening an ordinary box to framing leaves the marking missing, and the marking is what the inspector looks for.
• A luminaire inside a commercial cooking hood has to be identified for use in one, which covers construction, sealing and thermal shock together.
• Conductors direct buried with no raceway have to be identified for burial. A wet location rating answers a different question, since it covers a conductor sitting in water inside a raceway.
• An instantaneous trip circuit breaker serves as a motor branch circuit device only as part of a listed combination motor controller, because the coordination has to have been proved by the listing.
• Service equipment is listed or field evaluated for the use, and the marking at 230.66 records it. Nothing in that marking forces the equipment to be used at a service.

The same move works on the grounding items, where 250.118 recognizes certain flexible metal wiring methods as a fault path within stated limits and 250.146 releases the bonding jumper at a receptacle for a listed floor box. Those sit in the grounding and bonding area.

What it costs, and the Texas layer

On the job the cost is concrete. An unlisted item where a section asks for a listed one is a refusal at inspection and a return trip. A listed item installed against its instructions is the same refusal with a better paper trail, because 110.3(B) put those instructions inside the rule. Both of those are rework priced at your own labor.

The Texas layer decides who is doing the deciding. Approval belongs to the authority having jurisdiction under 90.4, and Texas runs on local adoption sitting on a state rule. 16 TAC 73.100 adopts the 2026 code with a state amendment at subsection (b), and Tex. Occ. Code 1305.201(c) and (d) leave cities their amendments and bind work inside the corporate limits to local ordinances. So two jobs twenty miles apart can meet different readings of the same equipment question in the same week, and asking early is the cheap move.

What a city cannot do is re-examine you or charge you a fee for working there, under Tex. Occ. Code 1305.201(b) and (f). Your license travels, while the approval decision on a given piece of equipment stays local, and the local rules page works through that split.

What to do before test day

This family rewards a short drill more than a long study session, because the work sits in four definitions and one habit.

1. Read the Article 100 entries for approved, identified, labeled and listed in your own book, and write the actor beside each one.
2. Read 90.7 once, so the question about factory wiring inside listed equipment answers itself on the day.
3. Tab 110.3 and 110.21, since both turn up as the general rule behind an equipment specific item.
4. When one of the four words appears in a stem, underline it before you look at the options.
5. Check the .2 section of any article you tab, because this edition put the listing requirement there and moved whatever used to hold that number.

The worked arithmetic behind the practice items, with the section printed under each answer, lives in the practice exam. This page stays with what a Texas candidate is tested on and what these words cost on a job here. For where the definitions sit in the structure of the book and who gets to interpret them, the Article 90 page comes first.

Questions people ask

What is the difference between listed and labeled?

Both turn on an organization acceptable to the authority having jurisdiction that evaluates products and keeps inspecting production, so the difference is where the evidence sits. A listing is a published record you can look up, naming the product or the manufacturer. A label is the mark on the item in your hand, applied by that same kind of organization. Neither word means approval, which under Article 100 is the authority having jurisdiction accepting the equipment. An exam option describing the manufacturer vouching for its own product misses both definitions at once.

Does a listing mean the inspector has to accept it?

No. Approval is the decision of the authority having jurisdiction, and 90.4 gives that person responsibility for approving equipment and materials. A listing is evidence that person usually leans on, so in practice most listed equipment is approved, and the words keep their separate meanings while that happens. The reverse also holds: equipment with no listing can be approved where the authority is satisfied by other evidence, because 90.4 also carries the power to permit alternatives where the objectives of the code are met by other means.

What does identified for the use actually ask for?

Something recognizable as suitable for the specific purpose the rule describes. Article 100 defines identified as applied to equipment in those terms, so suitability is the test and a marking or a listing is the usual way it gets shown. The word does narrower work than listed and broader work than approved. Candidates who read it as a demand for wording printed on the item rule out fittings that qualify, which is exactly the error the distractor is built from.

Are manufacturer instructions enforceable in Texas?

Where the equipment is listed or labeled, yes. 110.3(B) requires it to be installed and used according to any instructions included in the listing or labeling, which pulls the instruction sheet inside the rule. The standing example is a listed baseboard heater whose instructions rule out mounting below a receptacle outlet, because a cord hanging into the element is a fire. What instructions cannot do is authorize a departure from the code or settle an interpretation, because 90.4 leaves both of those with the authority having jurisdiction.

Where does the 2026 edition put listing requirements?

At the .2 section of an article, with reconditioned equipment at .3, because this edition ran a uniform section template through the book. That's the first place to look when you want to know whether an article requires the equipment it covers to be listed. And it explains a familiar section number turning up with unfamiliar text under it: an older citation for overcurrent protection at 450.3 now finds a reconditioned equipment heading with its subsections reserved, and the rules moved to 450.5. Informative Annex L tracks the moves.