Heat Treatment & ISPM-15: Export Pallet Compliance

What ISPM-15 Actually Regulates

ISPM-15 stands for International Standard for Phytosanitary Measures No. 15, published under the International Plant Protection Convention (IPPC). Its purpose is narrow and important: prevent solid-wood packaging material, pallets, crates, dunnage, and blocking, from carrying insects and fungi across borders in international trade. Untreated wood can harbor larvae that emerge in a new country with no natural predators, and the standard exists to shut that pathway.

The standard applies to raw or solid-wood packaging. It does not apply to processed wood products like plywood, oriented strand board (OSB), or particleboard, because the manufacturing heat and adhesives already destroy pests. Presswood or molded-wood pallets are likewise exempt for the same reason. This is why some exporters switch to engineered or plastic pallets specifically to sidestep treatment paperwork.

More than 180 countries participate in the IPPC framework, which is why an ISPM-15 mark is recognized at ports worldwide. It is a shared language of compliance, not a U.S.-only rule.

The 56C for 30 Minutes Rule

Heat treatment under ISPM-15 has a precise, non-negotiable target: the core of the wood, the coldest point in the thickest piece, must reach a minimum of 56 degrees Celsius (about 133 degrees Fahrenheit) and hold that temperature for at least 30 continuous minutes. It is the core, not the surface, that counts, because that is where a burrowing pest would survive.

Reaching that core temperature typically means running the wood in a treatment chamber for hours, not minutes, so heat has time to penetrate. Certified facilities use calibrated probes placed in sample boards to prove the coldest point crossed the threshold. The 30-minute clock only starts once that core probe hits 56C.

A crucial point of confusion: heat treatment is not the same as drying the wood to a target moisture content. The 56C/30-minute rule is a pest-kill specification, and a pallet can be ISPM-15 heat-treated while still being relatively 'wet' compared to a kiln-dried board.

Heat Treatment vs. Kiln Drying

People often use 'heat treated' and 'kiln dried' interchangeably, but they answer different questions. Heat treatment (HT) is about killing pests to a phytosanitary standard. Kiln drying (KD) is about removing moisture to reduce weight, prevent mold, and stabilize the wood dimensionally. A kiln can accomplish both, but only if it hits the ISPM-15 core-temperature profile.

The practical consequence: a KD stamp alone does not certify export compliance, and an HT stamp alone does not guarantee low moisture. If your buyer needs both dry and compliant wood, specify 'KDHT' or confirm the facility runs a schedule that satisfies the 56C/30-minute rule. Assuming one implies the other is a common and costly mistake.

Reading the Stamp: Anatomy of the IPPC Mark

A compliant pallet is branded, usually burned or stamped onto a stringer or block, with a standardized mark that inspectors can read at a glance. It is often called the 'wheat stalk' logo because of the stylized grain symbol beside the letters IPPC. Every element carries meaning.

• IPPC symbol: the encircled wheat-stalk logo confirming international compliance
• Country code: a two-letter ISO code (e.g., US) identifying where the wood was treated
• Facility/producer number: a unique identifier for the certified treatment provider, assigned by the national program (in the U.S., administered through the ALSC and its accredited agencies)
• Treatment code: HT for heat treatment, or the phased-out MB for methyl bromide; DB may appear for debarked material

The Methyl Bromide Phase-Out

The other historic treatment code is MB, methyl bromide fumigation. It kills pests effectively, but methyl bromide is an ozone-depleting substance regulated under the Montreal Protocol, and its use for wood packaging has been steadily curtailed and banned in many jurisdictions. The European Union, among others, no longer accepts MB-treated wood packaging on import.

For that reason, heat treatment is now the default and safest choice for exporters. If you see an MB stamp on a pallet, treat it as a warning sign for any shipment bound for a market that has phased the method out. When in doubt, HT is universally accepted where ISPM-15 applies, and it aligns with the sustainability priorities most shippers now carry.

What ISPM-15 Covers and What It Doesn't

The standard reaches further than pallets. It applies to solid-wood packaging material (WPM) of all kinds: crates, boxes, cases, dunnage, blocking, bracing, skids, and wood used to secure or cushion cargo. If it is raw or roughly processed wood that travels with your international shipment, it likely needs treatment and a mark.

Just as important is the list of exemptions, because they explain why some exporters switch materials to skip the paperwork entirely. Manufactured wood products are exempt because their production process already destroys pests, and very thin wood is generally excluded as well.

• Covered: pallets, crates, cases, dunnage, blocking, bracing, and skids in solid wood
• Exempt: plywood, OSB, particleboard, and other glued/processed wood products
• Exempt: presswood and molded-wood pallets (made under pest-killing heat)
• Generally excluded: wood 6 mm thick or less, and manufactured wood-based materials
• Switching to these exempt materials is one way exporters avoid treatment paperwork

Which Shipments Need It, and the Cost of Getting It Wrong

The dividing line is simple in principle: international shipments generally require ISPM-15-compliant wood packaging; purely domestic U.S. movements generally do not. If your product, or the pallet under it, is crossing a national border, you need the mark. Country-specific rules add nuance, so verify the destination's requirements before booking freight.

The penalties for non-compliance are entirely practical and entirely painful. Customs officials can refuse entry, order the shipment re-exported at your expense, require on-the-spot treatment or fumigation, or in some cases order destruction of the packaging and even the goods. Each outcome means delay, added cost, and a shipment that misses its window. Sourcing pre-stamped, certified pallets from a supplier who can prove treatment is cheap insurance against a five-figure port problem.

Two practical habits prevent almost all ISPM-15 problems. First, confirm the destination country's specific requirements before you book, since a few markets add rules beyond the baseline standard. Second, keep your treated and untreated pallet stocks physically separated in the yard, so an untreated unit never slips under an export load by accident. A supplier that stamps, tracks, and can document treatment for each batch removes that risk from your dock.