How to Find Out Whether Old Equipment Was Ever Listed

Why this matters

The question comes up at the worst moment: the customer wants a 1970s wall furnace reconnected after a remodel, an inspector asks whether the old baseboard heaters being moved were ever listed, or an insurer wants to know about a unit that was in a fire. Nobody in the shop knows, the plate is half painted over, and the manufacturer stopped existing before the tech was born. There is usually a way to find out, it takes days rather than minutes, and the answer matters less than people think until you know what you will do with it.

Before you start: what "was it listed" can and cannot settle

A listing means a recognized testing laboratory evaluated the product to a safety standard and kept it under follow-up inspection while it was made. See related: Listed, Labeled and Approved: Three Words That Are Not the Same. For old equipment, two cautions shape the whole search:

• Listed then is not compliant now. A listing was to the standard edition in force when it was made. A unit listed in 1974 met 1974's requirements and nothing written since. It also says nothing about the unit's condition after fifty years.
• The answer has to feed a decision. Existing equipment that stays where it is and is not altered is generally allowed to continue under the existing-building rules, as adopted. The listing question gets sharp when the unit is relocated, reconnected, reused in an alteration, or questioned after an incident. Know which of those you are in before spending a week on research.

The steps below run in order because each one is cheaper than the next, and each shows what it turned up on one real-shaped case: a gas-fired vented wall furnace the customer wants put back on line after a kitchen remodel. The data plate is inside the burner compartment, partly painted over.

Step 1: Make the appliance safe to read, then photograph everything

Do. For a gas appliance, the burner compartment cover comes off only with the gas valve off, the pilot out and the appliance cool; on an electric unit, the circuit is off at the breaker, locked and tagged, and proved dead with a meter checked on a known live source before and after (NFPA 70E Article 120 (120.5 in the 2021 edition, renumbered in 2024), with work practices at 29 CFR 1910.333(b)(2)). If you smell gas when the cover comes off, stop: everyone leaves the house, no switches, no lights, no phone use inside, and the gas utility gets called from outside. Then photograph the plate straight on, at an angle to catch stamped characters, and with a flashlight raking across it. Photograph every sticker, stamp and casting mark on the cabinet too.

Why. Paint and grime hide stamped numbers that raking light reveals, and a photo lets you zoom later without reopening the appliance. Old cabinets often carry the mark on a separate small label, not on the main plate.

If you skip it. You end up calling a lab with "a model number that starts with W and maybe a 4". Nobody can search that.

The case. The raking photo recovered the model number, a serial number, "Natural gas", an input rating of 35,000 Btu/h, and on the cabinet side a small round seal with a star, partly scraped.

Step 2: Read the plate for what it already tells you

Do. Transcribe every field: maker, model, serial, fuel, input, electrical rating, clearances, any date or date code, and every word near any mark ("Listed", "Certified", "Classified", "Recognized", a file or control number). See related: The Nameplate and What Every Field Tells You.

Why. A file number or control number is the key a laboratory searches by. The word next to the mark matters: "Recognized" or a component mark means a part inside was evaluated, not the appliance. See related: Recognized Components Versus Listed Products.

If you skip it. You will tell the customer "it's listed" because there is a logo, when the logo is on a component.

The case. No file number survived. The fuel and input fields were legible, and the clearances read "0 in sides, 6 in top" from what remained.

Step 3: Identify the mark, including marks that no longer exist

Do. Match the mark to the laboratory that used it. Some of what you will see on equipment from before the 1990s:

• The gas industry's star seal. For decades, gas appliances were certified by the American Gas Association's own laboratories, whose blue-star seal was the gas-appliance mark of its era. That certification business later moved to another testing organization, which holds the historical files.
• Older versions of current lab marks. Several labs changed their logos over the decades; an older mark is still that lab's mark.
• Marks from labs that no longer operate, or from labs that were never part of OSHA's Nationally Recognized Testing Laboratory program, which itself only began in 1988. See related: What a Nationally Recognized Testing Laboratory Is.

Why. The mark tells you whose files to search. Searching the wrong lab returns "no record", which people misread as "never listed".

If you skip it. A "no record" from the wrong source becomes a condemned appliance or, worse, a false all-clear.

The case. The star seal pointed to the gas laboratory's files, now held by its successor.

Step 4: Ask the manufacturer or its successor

Do. Find out whether the maker still exists or was absorbed. Old brands are frequently owned today by a larger company whose customer service or literature department keeps model-number histories. Ask for the installation and operating manual for the model, and whether the model carried a certification and from whom.

Why. The manual tells you the clearances and venting the listing was conditioned on, which you need anyway if the unit is going back in service. A maker's confirmation that the model was certified is also a document you can show an inspector.

If you skip it. You may get the lab's confirmation without the install conditions, which is half an answer for a reconnection.

The case. The brand had been bought out twice. The current owner's literature group had a scanned manual for the model series, which confirmed the clearances and showed the seal, but had no certification file.

Step 5: Ask the laboratory's records

Do. Search the lab's online certification directory first, but expect old and withdrawn files to be missing from it. Then contact the lab's customer service with the maker, model, serial and approximate year, and ask whether the model was covered by a certification or listing file, under which standard, and in which years. Ask for the answer in writing.

Why. Online directories generally show current certifications. Historical files are often held in records the lab will search on request, sometimes for a fee and usually in days or weeks rather than minutes.

If you skip it. "It's not in the directory" goes on the job record as if it meant "never listed".

The case. The successor lab's records confirmed, by email about two weeks after the request, that the model series had been certified under the gas wall-furnace standard of that era.

Step 6: Decide what you will do with the answer

Do. Write one sentence for the record and the customer: what was found, from whom, and what it means for this job. Then apply it.

The case. The answer was "certified in its era". That supported reconnection as far as the listing went; it did not settle condition. The inspector accepted the lab letter and the manual, and the shop reconnected only after its own safety checks: a gas leak test on the reconnected piping, inspection of the heat exchanger and vent, and a start-up with a personal CO monitor running and combustion and draft checked under the shop's gas start-up procedure before the customer was told it was back in service.

The same steps, opposite answer

A month later the same shop was asked to move four electric baseboard heaters from an old addition into a new bedroom. With each circuit off, locked, tagged and proved dead, the end covers came off. The plates were clean: maker, model, 240 V, 1,000 W each, and a lab mark with the word "Listed" and a file number. Step 4 found the maker still in business; step 5 found the file current for the maker's later models, but the lab's written reply said this model number did not appear in the file's history and had probably been sold under a private label from another plant.

So the mark was real and the file was real, and the heater in hand was still not shown to be covered. The shop priced new listed heaters at the same wattage for the new room rather than relocating units whose coverage could not be shown, and the customer chose the replacements. The lesson is in step 2: the file number on the plate identifies the file, not the model; only the lab can tell you whether the model sits inside it.

When you still cannot tell

Sometimes no step returns an answer: no mark, no maker, no file. Then treat the equipment as unlisted for any decision that needs a listing, and choose among:

• Leave it in place, unaltered, where the existing-building rules allow, and say plainly on the invoice what you could not establish.
• Field evaluation by an evaluation body the jurisdiction accepts, which is realistic for an expensive or irreplaceable item and rarely sensible for a common appliance. See related: Field Evaluation When a Product Has No Listing.
• Replacement, which is the usual answer for anything gas-fired or heat-producing whose provenance cannot be shown.

What you do not do is write "listed" or "certified" on the record because the unit looks like ones that were. That sentence is a claim, and it will be read back to you.

How to verify you got this right

The job record should hold the plate photos, the transcription, the identified mark and the source used for it, the maker's or successor's reply, the lab's written reply (or a note that none came and when you asked), and the one-sentence decision. Someone who was not on the job should be able to read it and reach the same answer.

References

• OSHA, Nationally Recognized Testing Laboratory program, 29 CFR 1910.7, for which laboratories are recognized today.
• 29 CFR 1910.333(b)(2) and NFPA 70E Article 120 (120.5 in the 2021 edition, renumbered in 2024), for de-energizing and proving dead before opening electrical equipment.
• The manufacturer's or successor's literature for the model, and the laboratory's records for its certification history.
• See related: Grandfathered Is Not a Permanent Status; The Product with a Mark Nobody Recognized.