What Is ISPM-15? A Plain-English Guide to Heat-Treated Export Pallets

Published January 14, 2026

If you ship products outside the United States on wood pallets, two letters decide whether your freight sails through customs or gets stuck at the border: HT. They stand for heat treated, and they’re the heart of a standard called ISPM-15.

Here’s what it actually means — without the jargon.

What ISPM-15 is

ISPM-15 (International Standards for Phytosanitary Measures No. 15) is a global rule that governs solid wood packaging material used in international trade — pallets, crates, wooden boxes, and dunnage. Its purpose is simple: stop invasive insects and plant diseases from hitching a ride inside raw wood as it moves between countries.

Almost every country that trades internationally enforces it. If your wood packaging doesn’t comply, the shipment can be refused, fumigated, returned, or destroyed — at your expense, and on your timeline.

How wood becomes compliant

There are two approved treatments, but heat treatment is by far the most common:

• Heat treatment (HT): the wood is heated in a kiln until its core reaches 56°C (133°F) for at least 30 continuous minutes. That’s enough to kill pests and larvae without any chemicals.
• Methyl bromide fumigation (MB): a chemical alternative that many regions are phasing out for environmental reasons.

Once wood is treated, it’s stamped and ready to ship. Importantly, heat treatment is about pest control, not strength — a heat-treated pallet isn’t stronger, it’s just certified safe for international transit.

Reading the stamp

A compliant pallet carries the IPPC mark (often called the “wheat stamp”). It tells inspectors everything they need to know:

• The IPPC logo (a stylized wheat symbol)
• A country code (e.g., US)
• A unique facility/certification number
• The treatment code — HT for heat treated

If a customs official can find and read that mark, your packaging clears. If they can’t, it doesn’t matter how carefully you packed the load.

Common mistakes that cause delays

• Assuming all pallets qualify. A standard domestic pallet is not ISPM-15 compliant unless it was heat-treated and stamped. You can’t retroactively stamp a pallet you already own.
• Mixing compliant and non-compliant wood. Every piece of solid wood in the shipment — including dunnage and blocking — must be compliant.
• Damaged or painted-over stamps. If the mark is illegible, the pallet is treated as non-compliant.
• Confusing HT with “kiln dried.” Kiln-dried lumber isn’t automatically ISPM-15 certified; the treatment has to meet the specific time-and-temperature standard and be stamped by a certified facility.

What this means for your business

If any of your freight crosses a border, the safest approach is to source heat-treated, ISPM-15 compliant pallets from a supplier that stamps them properly — and to make sure your crates and dunnage are compliant too, so the entire shipment is covered.

At APSS, we keep heat-treated, ISPM-15 pallets in stock and can build custom export-ready sizes, so your international shipments don’t get held up over packaging. Need a hand figuring out what your load requires? Get a quote or call us and we’ll point you the right way.