Heat-treated pallets and ISPM 15: what the stamp means and when you need it

ISPM 15 is the international standard for wood packaging that crosses borders. A compliant wood pallet is built from debarked wood, treated by an approved method, and stamped with the official IPPC mark by a producer that is registered in its country's program. You need it when you export to a country that requires it. You do not need it for shipments that stay inside the United States.

What ISPM 15 requires

The standard is published by the International Plant Protection Convention (IPPC), part of the UN Food and Agriculture Organization. Its treatment and marking annexes were last revised in 2018. It covers pallets, crates, boxes, dunnage, cable drums and spools made from raw wood. It has three parts: debarked wood, an approved treatment, and the mark.

In the U.S., the national plant protection organization is USDA APHIS. Under an agreement with APHIS, the American Lumber Standard Committee (ALSC) runs the heat treatment and methyl bromide programs, and producers must enroll with an ALSC-accredited inspection agency. You cannot make your own stamp.

Debarked wood

Pallets must be made of debarked wood, whatever treatment is used. Small, separate pieces of bark may remain if each one is:

• less than 3 cm wide (any length), or
• wider than 3 cm, with a surface area under 50 square cm.

Approved treatments

Code	Method	What the standard requires
HT	Heat treatment in a steam or dry kiln chamber	At least 56°C (about 133°F) for 30 continuous minutes throughout the whole piece, including the core
DH	Dielectric heating (microwave or radio frequency)	At least 60°C (140°F) for 1 continuous minute throughout the whole piece, including the surface
MB	Methyl bromide fumigation	A set concentration-time schedule over 24 hours at 10°C or warmer; no piece over 20 cm at its smallest cross-section
SF	Sulfuryl fluoride fumigation	A set schedule over 24 or 48 hours at 20°C or warmer; no piece over 20 cm; moisture content no higher than 75% (dry basis)

The APHIS export FAQ is clear that a pallet needs one treatment, not both: heat treatment to 56°C at the core for 30 minutes, or methyl bromide fumigation to the ISPM 15 schedule. Hardwood pallets must be treated and marked too.

Where methyl bromide stands

Methyl bromide is still an approved treatment, but the standard itself flags it. ISPM 15 notes that methyl bromide depletes the ozone layer, encourages countries to promote the alternative treatments, and reminds them of their obligations under the Montreal Protocol. If you have a choice, HT avoids the fumigant question entirely.

What is exempt

ISPM 15 does not apply to:

• wood packaging made entirely of wood 6 mm thick or less
• packaging made wholly of processed wood such as plywood, particle board, oriented strand board or veneer made with glue, heat or pressure
• sawdust, wood shavings and wood wool
• wood components permanently attached to freight vehicles and containers

Plastic and metal pallets are not wood packaging, so the standard does not cover them.

Who needs ISPM 15 pallets

Exporters. APHIS keeps a list of countries that have told it in writing that they require ISPM 15 wood packaging. It includes Mexico, the European Union, the United Kingdom, Japan, Australia, Brazil and India, among others. APHIS says the list is not all-inclusive, so check your destination's rules before you ship.

Shipments to Canada. The U.S. and Canada exempt wood packaging made from wood that originated in the continental United States or Canada. To use the exemption, APHIS says your import documentation must include the statement "The wood packaging material originated in the Continental US." Canada's food inspection agency confirms that wood packaging from the continental U.S. is exempt from its import directive. Wood packaging from any other origin must meet ISPM 15.

Domestic shipments. ISPM 15 is a standard for international trade, so it is not required for loads that stay in the U.S. APHIS also says treatment and the mark are not required for wood packaging shipped from the U.S. mainland to Hawaii, Puerto Rico and U.S. territories. Some customers still write HT into their own pallet specs. If yours does, buy to the spec.

How to read the stamp

Every compliant mark has four required parts:

1. The IPPC symbol (the wheat-ear logo), on the left.
2. The country code, the ISO two-letter code (US for the United States).
3. The producer or treatment provider number, assigned under the national program and joined to the country code with a hyphen.
4. The treatment code: HT, DH, MB or SF, on its own line or after another hyphen.

A typical U.S. layout looks like this, with the symbol in the left box:

| [IPPC symbol] | US-0000 |
|               | HT      |

The standard also sets rules for how the mark is applied. It must sit inside a rectangular or square border with a vertical line between the symbol and the codes. It must be legible, durable and not transferable, and placed where it is visible in use, preferably on at least two opposite sides. It must not be hand drawn, and red or orange should be avoided because those colors are used for dangerous goods labels. Nothing else may sit inside the border.

U.S. marks usually carry a few extras. The accredited agency's logo or name appears outside the border. "DUN" is added when the wood is dunnage. Under the ALSC policy, "KD" can appear with HT when the lumber was also kiln dried, which ALSC defines as a maximum moisture content of 19% at the time of surfacing.

Recycled and repaired HT pallets

A recycled pallet can still be compliant. ISPM 15 says a treated and marked unit that has not been repaired, remanufactured or otherwise altered does not need to be re-treated or re-marked during its service life. APHIS puts it simply: the treatment does not expire.

Repairs change that:

• Repaired (up to about one third of components replaced): only treated wood (or exempt processed wood) may be used, and each added treated component must carry its own mark.
• Remanufactured (more than about one third replaced): old marks must be permanently obliterated, and the whole unit must be re-treated and re-marked.

In the U.S., ALSC rules are stricter for repaired pallets: the old mark must be obliterated unless the repair facility has an agency-approved process showing every component was treated, and the pallet can be re-marked only after heat treatment.

When you receive recycled HT pallets for export, look for clean, legible marks and check that replacement boards carry marks of their own. Add both checks to your receiving inspection. A painted or hand-lettered "HT" is not a valid mark.

What heat treatment does not do

HT is a pest measure. ISPM 15 states that its measures are not intended to provide ongoing protection from contaminating pests or other organisms after treatment. Heat treatment also says nothing about moisture unless the stamp includes KD. Store HT pallets dry and inspect them before loading, especially for food or pharmaceutical exports.

What HT costs and how to order it

Heat treatment is priced as an adder on top of the base pallet. On our current delivered ranges for 48x40 truckloads, the HT adder is $1.00–$1.50 per pallet (as of October 15, 2026). See current prices for the base grades and use the truckload calculator to price a full load.

When you request a quote, say "ISPM 15 HT" in writing, give the destination country, and ask whether the supplier can send a heat-treatment certificate with the load. Under ISPM 15 the mark itself is the proof; the standard says the mark makes a phytosanitary certificate unnecessary, and APHIS does not issue phytosanitary certificates for pallets used to carry goods. Some customers and forwarders still ask for supplier paperwork, so it is worth having. Chesapeake Pallets (our sister company) sells heat-treated 48x40s by the full truckload as an adder, and its heat-treatment certificate is available on request.

FAQ

Do I need heat-treated pallets for domestic shipments?

No. ISPM 15 applies to wood packaging in international trade. You only need HT on a domestic load if your customer's pallet spec calls for it.

Do I need ISPM 15 pallets to ship to Canada?

As of October 2026, not if the pallets are made from wood that originated in the continental U.S. or Canada and your import documents include the origin statement APHIS specifies. Pallets of any other origin must be ISPM 15 compliant. The two countries have discussed phasing in full ISPM 15 for cross-border trade, so check APHIS before you ship.

Does the HT stamp expire?

No. A treated and marked pallet keeps its status for its service life unless it is repaired or remanufactured. After repairs, U.S. rules generally require the old mark to be obliterated and the pallet re-treated before it is re-marked.

What is the difference between HT and KD?

HT means the wood core reached at least 56°C for 30 continuous minutes, which is a pest treatment. KD means kiln dried to a maximum moisture content, which ALSC sets at 19% at the time of surfacing. A stamp can show both.

Are plastic or plywood pallets exempt from ISPM 15?

Yes. The standard covers packaging made from raw wood. Plywood, particle board and OSB made with glue, heat or pressure are exempt, and plastic pallets are not wood packaging.