The short answer
The stamp is four fields, not a logo. The convention’s symbol, a two-letter country code, the producer number a national authority issued, and a treatment code such as HT.
Most rejections are not treatment failures. They come from a mark nobody can see inside a loaded container, untreated wood added to a treated crate, or a repaired pallet that never got re-marked.
A wooden pallet crossing a border carries a stamp, and an inspector reads that stamp before anyone opens the paperwork. Four small fields hold the entire plant-health claim for the wood underneath.
The treatment behind the mark is well understood. Heat the wood until its core reaches 56°C and hold it there for thirty minutes. What actually catches exporters sits around that number rather than inside it.
This reference covers what the mark must contain, the four approved treatments, and which wood falls outside the rules. It also covers the repair and marking mistakes that turn a container back.
What the Mark Has to Carry
The rule sits in Annex 2 of the standard, and it is short. Four components, in a bordered mark.
- The symbol — the convention’s own mark, which signals the whole scheme.
- Country code — the two-letter ISO code for the country where treatment happened.
- Producer code — the unique number the national plant protection organization assigned to that facility.
- Treatment code — HT, DH, MB or SF, naming which method the wood went through.
None of the four is optional, and a mark missing one of them is not a mark.
Three conditions travel with those fields. The mark has to be legible, it has to be durable and not transferable, and it must not be hand drawn.
That last clause rules out the marker-pen stamp that turns up on repaired pallets. A mark applied by hand is not a deficient mark; it is not a mark at all.
The mark’s structure, annotated. A pen-and-hand version fails on the fourth condition alone.
The Four Approved Treatments
Most guides name heat and methyl bromide, yet Annex 1 lists four. Each carries its own parameters, and two carry a limit on how thick the wood may be.
| Code | Treatment | Parameter | Limit |
|---|---|---|---|
| HT | Heat treatment | 56°C for 30 continuous minutes throughout the profile, core included | — |
| DH | Dielectric heating | 60°C for 1 continuous minute throughout the profile, surface included | — |
| MB | Methyl bromide | 650 g·h/m³ over 24 hours at 21°C or above; colder wood needs more | Cross-section over 20 cm not permitted |
| SF | Sulphuryl fluoride | 1,400 g·h/m³ over 24 hours at 30°C or above | Over 20 cm, or moisture above 75%, not permitted |
Two details in that table get lost in most write-ups. Heat treatment specifies the core, while dielectric heating specifies the surface, because the two methods heat wood from opposite sides.
Fumigation temperature matters as well. The concentration-time product for methyl bromide rises as the wood gets colder, so a winter treatment at the summer dose has not met the standard.
Where the Mark Goes
Placement is the failure mode nobody writes about. The standard asks for the mark in a location that stays visible while the packaging is in use, preferably on at least two opposite sides.
Read that wording carefully, because “preferably” is the standard’s own word, which makes two sides a strong recommendation rather than a flat mandate.
The reason appears in the IPPC’s explanatory document, which favors marking twice on opposing vertical faces so inspectors can read it inside a loaded container. One stamp facing a container wall is an unreadable stamp.
Destination authorities still decide what they accept. The same document notes that countries demanding measures beyond the standard owe a technical justification, which limits them, but leaves them the final say.
US exporter guidance puts it plainly: the mark must be legible and easily visible on each piece, preferably on two opposite sides.
The fix is cheap: ask the supplier to mark both faces, and the argument never starts.
Kiln Dried Is Not Heat Treated
Kiln-dried lumber and heat-treated lumber come out of similar equipment, and the marks sit side by side in a grade stamp, yet they certify different things.
Drying targets moisture content. Heat treatment targets a temperature held at the core, which NELMA states as 56°C, or 133°F, for thirty minutes in every solid wood component.
A KD-HT mark covers both, meaning heat treatment plus drying to 19 percent moisture or less, while KD on its own covers only the drying.
So a kiln schedule that never drives the core to 56°C produces dry wood that carries no plant-health claim at all. Dry is not the same as treated, and customs reads the treatment code.
What Counts as Regulated Wood
Solid wood packaging is in scope, though several categories sit outside it, and knowing which of them saves needless treatment cost.
Wood 6 mm or less in thickness is exempt. So is processed wood material: the standard names plywood, particle board, oriented strand board and veneer, because the mill already put those through heat and glue.
The exemption list runs further, covering barrels heated during manufacture, processed gift boxes, sawdust, shavings and wood wool, plus wood components permanently attached to vehicles.
Dunnage is firmly in scope, and the explanatory document flags it as the harder case, since dunnage is often large timber that resists even heating. Loose blocking and bracing needs the same mark as the pallet under it.
One more trap sits in the word solid, because a box built from plywood panels is exempt while the frame under it may be solid wood. Mixed builds need the solid parts marked.
Bark has its own tolerance rather than an outright ban. Small separate pieces may remain where each is under 3 cm wide, or where a wider piece covers less than 50 square centimetres.
Timing differs by method too: fumigation requires debarking beforehand, while heat treatment allows it either before or after.
Repair, Remanufacture and the One-Third Line
A pallet that gets a new board is a different question from a pallet rebuilt out of salvage. The standard draws the line at roughly a third of the components.
Below that line the item counts as repaired. Only treated wood or processed wood material may go in, and each added component needs its own mark, so a single replacement board carries its own stamp.
Above that line the item counts as remanufactured. The old marks come off for good, the whole item goes back through treatment, and a fresh mark goes on.
National authorities may tighten the repaired case toward the remanufactured one. APHIS guidance takes that route for the United States. Repaired or remanufactured packaging goes back through treatment, the old mark comes off, and an inspection agency applies a new one.
Nobody Stamps Their Own Pallets
The mark is not artwork a shipper can order. In the United States the American Lumber Standard Committee runs the program under a memorandum with APHIS, through fifteen accredited third-party agencies and separate schemes for heat treatment and fumigation.
Producers enroll with one of those agencies, and registered facilities apply the mark to finished pallets and crates. Self-marking is not a shortcut with paperwork attached; it is counterfeiting.
Altering certified packaging breaks the claim just as thoroughly. APHIS tells exporters not to modify certified material or mix it with uncertified material, which means one untreated block added to a compliant crate compromises the load.
What follows is worth knowing, since the same notice points to administrative orders, civil penalties and, at the serious end, felony convictions under the Plant Protection Act. Blame can also run back to whoever supplied the altered material.
Costs land on the exporter rather than the supplier. That notice warns that shippers using noncompliant material may meet fees, fines and even bans from trading partners.
The cheap fixes all happen before the load leaves, so check that both faces carry a mark and that every loose block and brace carries one too. Check also that no board has changed since the stamp went on.
None of that needs a lab or a form, just someone to walk the load and look at it.
Common Questions
Do plastic or plywood pallets need an ISPM 15 stamp?
Plastic is not wood, and plywood counts as processed wood material, so neither needs the mark. A plywood case sitting on solid wood skids is a different matter, because those skids need treatment and marking.
Does the stamp mean the pallet is strong enough for the load?
No. The mark is a plant-health declaration and says nothing about load capacity, deck stiffness or grade. Standard pallet sizes and load ratings are a separate specification entirely.
Can a certified pallet be cut down to fit a load?
Cutting is an alteration, and it breaks the certification on that item. The modified piece needs treatment and a fresh mark from an accredited agency before it crosses a border again.
Does a treatment mark expire?
The standard sets no expiry date, so a mark holds while the item stays unaltered and the mark stays legible. An inspector can still reject wood that got re-infested or damaged after treatment.
What the mark does not claim. It is a phytosanitary declaration about the wood, nothing more. It carries no grade, no load rating and no cleanliness statement, and rules at the destination change, so the importing country’s current rules govern any shipment.
Key takeaways
- The mark carries four fields: the convention’s symbol, a two-letter country code, the producer number and a treatment code.
- Four treatments are approved, and each specifies its own parameters, with methyl bromide and sulphuryl fluoride limited to wood under 20 cm in cross-section.
- Placement decides readability, and the standard asks for the mark preferably on two opposite sides so inspectors can see it inside a loaded container.
- Kiln drying is not heat treatment; KD-HT covers both, while KD alone certifies moisture content and no plant-health claim.
- Repairs above roughly a third of components trigger obliteration, re-treatment and re-marking, and only accredited facilities may apply the mark.