Heat-treated pallet: ISPM 15 HT explained
A heat-treated (HT) pallet is a wood pallet whose wood has been heated until its core reached 56 °C (133 °F) for at least 30 continuous minutes, as required by ISPM 15, and then stamped with the IPPC mark and the code HT. Many countries require ISPM 15 treatment for wood packaging crossing their borders.
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What is a heat-treated pallet?
A heat-treated pallet meets the ISPM 15 standard for wood packaging material by heat treatment. ISPM 15 exists to stop wood-boring insects and other pests from traveling in pallets and crates. Treatment kills them; the mark proves it.
ISPM 15 treatment methods
| Code | Method | Requirement |
|---|---|---|
| HT | Heat treatment | Core of the wood at 56 °C for 30 continuous minutes |
| DH | Dielectric heating | 60 °C for 1 continuous minute throughout the profile |
| MB | Methyl bromide fumigation | Being phased out; banned in some countries |
| SF | Sulfuryl fluoride fumigation | Fumigant alternative |
Wood must also be debarked. Small bark remnants are allowed: pieces under 3 cm wide of any length, or wider pieces with a surface area under 50 cm².
What the HT stamp shows
The ISPM 15 mark reads left to right:
- The IPPC wheat-ear symbol.
- The two-letter ISO country code, e.g. US.
- The producer or treatment-provider number issued under the national plant protection organization. In the US these come through ALSC-accredited agencies.
- The treatment code: HT, DH, MB or SF.
The mark must be legible, permanent and inside a border. Put it on at least two opposite sides. Costco asks for both long sides and Snap-on recommends all four; confirm with the current vendor guide.
KD vs HT
A KD (kiln-dried) stamp is about moisture, not pests, and is not ISPM 15 compliance. A kiln can deliver both, which is marked KD-HT. See kiln dried vs heat treated.
| HT | KD | |
|---|---|---|
| Purpose | Phytosanitary (pests) | Moisture content |
| Standard | ISPM 15 | Buyer spec (e.g. 19% MC) |
| Mark | IPPC symbol + HT | KD or KD19 |
| Satisfies export rules | Yes | No, unless also HT |
When you need a heat-treated pallet
- Exports. Most countries enforce ISPM 15 on imported wood packaging. See export pallets.
- US to Mexico: HT is required. Canada to US: not required at that border, according to Costco's pallet policy.
- EPAL pallets: ISPM 15 heat treatment has been part of the EPAL 1 specification since 2010.
- Customer requirement even for domestic use.
When you don't
- Domestic shipments with no customer requirement.
- Wood 6 mm thick or less, and processed wood such as plywood, OSB and particleboard, which are exempt.
- Plastic, metal and paper pallets, which are exempt as non-wood.
Repairs and re-treatment
Repaired, remanufactured and combo pallets must be re-treated and re-marked, with old marks obliterated. An intact compliant pallet can be reused without re-treatment.
How to specify a heat-treated pallet
- "ISPM 15 HT" (or DH) on the spec.
- Mark locations: two sides, two long sides, or all four.
- Whether a certificate or letter of compliance is required.
- Moisture: HT alone, or KD-HT with a target moisture.
- The rest of the pallet spec: size, construction, lumber, load.
In palletdesign.ai the HT flag is part of the lumber spec: it adds heat treatment to the indicative cost and to the classification line on the drawing, and the rules block an export design without it.
Questions
- What temperature is ISPM 15 heat treatment?
- The core of the wood must reach 56 °C (133 °F) and stay there for at least 30 continuous minutes.
- Is kiln-dried the same as heat-treated?
- No. Kiln drying targets moisture content; heat treatment under ISPM 15 targets pests and earns the HT mark. A pallet can be both, marked KD-HT.
- Do repaired pallets need to be re-treated?
- Yes. Repaired, remanufactured and combo pallets must be re-treated and re-marked, with the old marks removed.
- Do plywood pallets need heat treatment?
- Plywood and OSB are exempt as processed wood, but any solid-wood parts on the same pallet must be treated.
Related
- ISPM 15: heat treatment and marking for export palletsISPM 15 requires export wood pallets to be debarked and treated, usually heat treated to 56 °C core for 30 minutes, and stamped with the IPPC mark.
- Heat treatmentHeat treatment (HT) heats pallet wood until its core reaches 56 °C for 30 minutes, the ISPM 15 treatment that lets wood pallets cross borders. Marked HT.
- ISPM 15 markThe ISPM 15 mark is the stamp showing wood packaging was treated for export: the IPPC wheat symbol, country code, producer number and treatment code such as HT.
- Kiln-dried vs heat-treated palletsKiln drying lowers moisture (often to 19%); heat treatment is the ISPM 15 export treatment (56 °C core for 30 min). KD alone is not ISPM 15 compliant.
- Export pallet: what international shipments requireAn export pallet must meet ISPM 15 (heat treated and stamped) if made of solid wood, and should match the destination's footprint. Options, sizes and specs.
- Custom pallet: how to design and specify oneA custom pallet is built to a buyer's own size, load and handling needs rather than a stock design. What drives the design and the fields a quote needs.