Intertek Warnock Hersey Wood Stove Certification Explained

Warnock Hersey (WH) is a safety-testing mark owned by Intertek, not a stove brand. When it appears on a wood stove label, it means a third-party lab tested and listed that model. It does not tell you who built the stove, how clean it burns, or that your installation is safe.

That gap is where most searches go wrong. People type a model number plus “Warnock Hersey” looking for specs or a manual, when the lab does not hold either. This guide explains what the mark proves, how to read the rest of the label, where the listing stops and your installation begins, and how to track down your stove’s real maker.

What the Warnock Hersey Mark Means

Intertek describes the Warnock Hersey and ETL marks as two ways of showing that a product was independently tested and certified to applicable safety standards, with equal acceptance across North America. The WH name comes from Canadian testing labs: Intertek Canada’s own history says Hersey and Warnock merged their businesses in 1954, and the combined lab later became part of Intertek.

For a stove, the mark sits on the rating label next to the test standards. A real example is the label printed in the owner’s manual for Enviro (Sherwood Industries) models 1000, 1600, 1600 INS and 2100, which reads “listed solid fuel space heater” and “tested to CSA B366.2/ULC-S627, ULC-S628-M93, UL-1482-1994.” The same manual says the stoves were tested and listed by Intertek (WH).

How to Read a Stove Rating Label

The label is a legal document for your installation, not decoration. Using the Enviro label as the worked example, here is what each line is telling you:

Line on the label	What it tells you	What to do with it
Listed solid fuel space heater	A lab tested it as a solid-fuel room heater	Confirms it is a listed appliance, not a decorative or unlisted unit
Tested to CSA B366.2/ULC-S627, UL-1482	The safety standards used (Canada and U.S.)	Look these up if an inspector asks what the stove was tested to
Report number	The lab’s test record for that model	Quote it, with the model and serial number, when contacting the maker
Install and use only in accordance with the manufacturer’s instructions	The listing depends on following the manual	Keep the manual; do not improvise
Contact local building or fire officials	Local rules and inspection still apply	Ask before you install, not after
Minimum clearances to combustible materials	The distances proven safe in testing	Measure your actual walls and ceiling against them
Chimney connector and chimney type	The venting the test assumed (for example a 6 in. connector and a listed chimney)	Match it; do not downsize or swap pipe types
Do not remove this label	The label has to stay with the stove	Photograph it for your records and leave it in place

One more detail from that same label: the model 1000 is marked suitable for mobile homes, and the manual says the model 1000 and 1600 freestanding units were tested and listed for mobile home use. The 1600 INS insert and the 2100 are not in that statement. A listing is model-specific, so never assume one stove’s approval covers its siblings.

The Myth: “Warnock Hersey Means It Meets Code and EPA Rules”

Three separate things get blurred together on the internet, and they are worth pulling apart:

• Safety listing (the WH/ETL mark). The stove was tested to a safety standard such as UL 1482 or ULC-S627, which sets the clearances printed on the label.
• EPA emissions certification. A separate approval with its own permanent EPA label. EPA’s Step 2 limit, in effect since 2020, is 2.0 grams of particulate per hour when tested with crib wood, or 2.5 g/hr if the maker tested with cord wood. The 2015 Step 1 limit was 4.5 g/hr, and EPA says older uncertified stoves can release 15 to 30 grams of smoke per hour.
• Your installation. Chimney, hearth protection, and clearances are inspected locally. A listed stove installed too close to a wall is still an unsafe installation.

So a WH label by itself says nothing about emissions. To check that part, look for the EPA label on the back of the stove and look the model up in EPA’s certified wood heater database. Read more about burn habits in our guide to how to burn wood safely.

Listed vs. Unlisted: Why Clearances Matter So Much

The practical value of a listing is that the lab already measured how hot nearby surfaces get, so the maker can print short clearances. An unlisted stove has no such data, so the installer falls back on generic code distances. The Maine State Fire Marshal’s installation guide, which cites NFPA 211 (1996 edition), shows the difference:

Item	Unlisted radiant stove (no added protection)	Listed stove
Walls, ceiling, front, rear and sides	36 in.	As printed on the stove label and in the manual
Stovepipe connector to combustibles	18 in.	As printed on the label (the Enviro example shows 18 in. from a horizontal connector and ceiling)
Floor	Depends on leg length: under 2 in. needs a fire-resistant floor; 2 to 6 in. needs 4 in. hollow masonry plus 24-gauge sheet metal; over 6 in. needs 2 in. masonry over 24-gauge sheet metal	Per the label and manual

The same guide allows reduced clearances for an unlisted stove when the wall is protected. For example, 24-gauge sheet metal on a ventilated air space is rated for a 66 percent reduction, which turns 36 inches into 12 inches, and the shield needs at least a 1 in. air gap. Treat this as a worked example of how the system works, not as permission: the guide is based on a 1996 edition, so confirm current code and your local official before building any heat shield.

If you are planning a wall shield or hearth, see our guide to insulating around a wood stove and our notes on venting a wood burner.

Looking Up a Model Number, Serial Number, or Manufacture Date

Warnock Hersey and Intertek are the labs that tested and listed the product. They are not the manufacturer and they do not keep a public database of stove specifications. Numbers like “S171E,” “WH200,” or a six-digit code are meaningless to the lab unless you know which maker they belong to.

• Find the metal label (usually the back, side, or underside) and photograph it.
• Write down the manufacturer name, model, serial number, and any report number.
• Go to that manufacturer’s website or customer support line for the manual, parts diagram, and manufacture date. Date-code schemes differ by maker.
• If the label is unreadable, a local hearth dealer can often identify a stove from its firebox shape, door style, and legs.

The Enviro manual makes the same point about parts: it tells owners to contact their local Enviro dealer when replacement parts are required. For one example of a maker with a long product line, see our Pacific Energy wood stove reviews.

Keeping a Listed Stove Inside Its Limits

The listing assumes you run the stove as designed. A few habits keep you within that:

• Burn dry wood. Wet fuel smolders and builds creosote in the flue. Our longest-burning fire logs guide covers fuel options.
• Do not overfire. Running far hotter than the manual allows is how stoves warp and surfaces near them overheat. A stove-top thermometer is the cheap way to watch it; see can a wood burner get too hot.
• Inspect the chimney yearly. NFPA 211 says chimneys, fireplaces, and vents should be inspected at least once a year for soundness, freedom from deposits, and correct clearances.
• Use the maker’s parts. Gaskets, glass, and firebrick are specified for each model, so order by the model number on the label.
• Keep the label legible. It is the proof of what the stove is listed for.

Conclusion

The Warnock Hersey mark tells you a lab listed the stove to a safety standard. The rest of the label tells you how to install it, and the EPA label tells you how clean it burns. Check all three, follow the clearances, and talk to your local building or fire official before you light it. Browse more guides in our Wood Burning Solutions hub.

FAQs About Intertek Warnock Hersey Wood Stoves

What does the Warnock Hersey mark mean on a wood stove?

It means Intertek, a third-party testing lab, listed the stove as having passed safety testing to the standards named on its label (for example UL 1482 in the U.S. and ULC-S627 in Canada). It is a lab mark, not a brand, and it is not an emissions rating.

How can I tell if my stove is Warnock Hersey listed?

Read the metal rating label on the stove. A listed stove carries the lab mark, a statement such as listed solid fuel space heater, the standards it was tested to, a report number, and the clearances to combustibles. If you cannot find or read it, contact the manufacturer with the model and serial number.

Is a Warnock Hersey stove also EPA certified?

Not automatically. The safety listing and the EPA emissions certification are two separate approvals. EPA-certified stoves carry their own permanent EPA label, and you can check the model in EPA’s list of certified wood heaters.

Can Warnock Hersey or Intertek give me my stove’s manual or specs?

No. They tested and listed the product, but the manufacturer holds the manual, parts diagrams, and specifications. Use the maker’s name and the model number from the same label.

Do I have to follow the clearances printed on the label?

Yes. A listing only applies when the stove is installed and operated as the manual and label say. The label also tells you to contact local building or fire officials about restrictions and inspection in your area.

How often should a listed wood stove and its chimney be inspected?

NFPA 211 calls for chimneys, fireplaces, and vents to be inspected at least once a year for soundness, freedom from deposits, and correct clearances. A chimney sweep can do this when cleaning the flue.