ISPM-15 and Exporting: Everything About the HT Stamp

Ship a wooden pallet across almost any international border without the correct ISPM-15 mark and you invite an expensive outcome: fumigation at port, forced re-export, destruction of the pallet, or refusal of the entire shipment. ISPM-15 is the global rule that governs wood packaging in international trade, and the small stamp burned into a compliant pallet is the passport that lets your freight through. This guide covers what the standard requires, how heat treatment works, and how to read and trust the mark.

What ISPM-15 is and why it exists

ISPM-15 (International Standards for Phytosanitary Measures No. 15) is a regulation developed under the International Plant Protection Convention (IPPC). Its purpose is narrow but important: prevent solid-wood packaging from carrying tree-killing pests, larvae, and fungi from one country to another. The standard applies to solid wood packaging thicker than 6 mm, which includes almost all pallets, crates, and dunnage. It does not apply to processed wood products like plywood or oriented strand board, because manufacturing already sterilizes them.

The two approved treatments

Code	Treatment	Requirement	Status
HT	Heat treatment	Wood core reaches 56C for at least 30 continuous minutes	Standard, widely used
MB	Methyl bromide fumigation	Chemical fumigation to a prescribed dosage	Being phased out; banned in many regions

Heat treatment (HT) is now the dominant method. The wood is placed in a kiln and heated until the core of the wood reaches 56 degrees Celsius and holds there for a minimum of 30 minutes. That core temperature, not the surface or the air temperature, is what kills pests. Methyl bromide (MB) is a fumigant that is being phased out globally because it depletes the ozone layer and is toxic; many countries no longer accept it at all, so HT is the safe default for exporters. For the full process, see our heat-treatment page.

A common misconception: heat treatment is not the same as kiln drying. Kiln drying reduces moisture content but may never reach the pest-killing core temperature. Only the certified 56C-for-30-minutes cycle satisfies ISPM-15.

Anatomy of the IPPC stamp

A compliant pallet carries a mark, burned or stenciled onto the wood, that is legible and permanent. It contains several required elements:

• The IPPC symbol: a stylized wheat or leaf logo inside a box on the left. This is the mark that certifies the standard.
• Country code: a two-letter ISO code (for example US for the United States) identifying where treatment occurred.
• Producer or facility number: a unique registration number assigned to the treating facility by the national plant protection organization.
• Treatment code: HT for heat treatment or MB for methyl bromide. You may also see DB (debarked) as a supplementary indicator.

A typical mark reads something like the IPPC logo, then "US - 123456", then "HT". No phone number, no company logo, no marketing text belongs inside the certified box. If you see extra decorative content crammed inside the IPPC symbol box, treat it with suspicion. For a detailed walkthrough of every element, read how to read a pallet stamp.

Compliance checklist for exporters

1. Confirm every wooden pallet, crate, and piece of dunnage in the shipment carries a legible IPPC mark.
2. Verify the treatment code is HT unless the destination specifically accepts MB.
3. Check that the mark is on at least two opposite sides so it is visible however the pallet is positioned.
4. Reject pallets where the mark is illegible, painted over, or partially cut away by damage.
5. Keep documentation matching the treatment facility number to your supplier.
6. Remember that repaired pallets must be re-marked; a repair with untreated wood invalidates the original stamp.

Repairs, remanufacturing, and the mark

ISPM-15 has strict rules about repairs. If a compliant pallet is repaired with new components, every added piece of wood must itself be treated, and in many jurisdictions the pallet must be re-treated and re-marked as a whole, with the old mark obliterated. This matters because a recycled pallet that looks stamped may have been repaired with untreated boards after the stamp was applied. When buying export pallets from a recycler, confirm the treatment and repair chain. This is one area where sourcing from a knowledgeable yard pays off.

What non-compliance costs

Failure mode	Typical consequence
Missing or illegible mark	Hold at port; on-site fumigation fees
Wrong treatment for destination	Refusal of entry; forced re-export
Live pest found	Destruction of packaging, sometimes the goods
Repeat violations	Enhanced inspection of future shipments

Any of these can blow a delivery schedule and erase the margin on a shipment. The stamp is cheap insurance.

The Tucson takeaway

If your freight leaves the country, plan for ISPM-15 from the start. Specify HT-treated pallets, verify the IPPC mark before loading, and be especially careful with repaired recycled units. We can supply properly heat-treated pallets and build new custom export crates with compliant marks. For a full breakdown of stamp elements, keep this reference handy, and check the FAQ for common export questions.

Exporting soon? Let us supply compliant HT-stamped pallets so your freight clears customs cleanly. Request a quote or contact our Tucson yard.