Heat treatment is a critical process for pallets used in international shipping and certain domestic applications. Learn about the ISPM-15 standard, the heat treatment process, stamp requirements, and how to ensure compliance.
What Is Pallet Heat Treatment?
Pallet heat treatment is a phytosanitary process meant to kill insects, larvae, and pathogens that may be present in wood packaging. Under ISPM 15, the core of the wood must reach at least 56 degrees Celsius (132.8 degrees Fahrenheit) for at least 30 continuous minutes.
The need for treatment grew out of real damage caused by pests moving in wood packaging. The Asian long-horned beetle, the emerald ash borer, and the pine wood nematode are among the invasive species linked to untreated wood packaging, which led to international rules for wood packaging materials.
Methyl bromide fumigation is the older alternative. It is an ozone-depleting substance, and a number of countries restrict it or no longer accept it, so check current regulations for your destination. Heat treatment is the method most exporters use.
The ISPM-15 Standard
ISPM 15, International Standards for Phytosanitary Measures No. 15, is the international standard for wood packaging materials in trade. It was adopted under the International Plant Protection Convention (IPPC) and applies to pallets, crates, and dunnage made from raw wood.
Most countries the United States trades with require ISPM 15 compliance, though rules and exceptions differ by destination and change over time. Non-compliant shipments can be refused entry, held, treated, destroyed, or sent back at the shipper's expense, along with missed delivery dates and unhappy customers.
In the United States, the program falls under APHIS (the Animal and Plant Health Inspection Service), working with accredited agencies that approve treatment facilities. Only approved facilities may apply the ISPM 15 mark.
The Heat Treatment Process in Detail
Pallets are loaded into a treatment chamber, which may be a kiln, a converted container, or a purpose-built room. The chamber is heated until the core of the thickest wood reaches 56 degrees Celsius, and temperature probes in representative pieces confirm the core temperature is held for the full 30 minutes.
Chamber size and total cycle time vary with the equipment, the moisture in the wood, the outside temperature, and the size of the load.
Humidity control matters too. Very dry conditions can cause surface checking and splitting, while very humid conditions can lengthen the time needed to reach core temperature.
Understanding the HT Stamp
Heat-treated pallets carry a mark with several pieces of information. The IPPC logo, a stylized wheat symbol, shows the pallet was treated under the international standard. A two-letter country code identifies where treatment took place (US for the United States), and a unique number identifies the treatment provider.
The code HT shows heat treatment was used. DB indicates debarked wood. The mark must be legible and permanent, and it is typically applied on at least two opposite sides so it is visible however the pallet is oriented.
Misusing the mark is a serious matter. Approved treatment providers keep treatment records for each batch, and those records can be audited. Ask your supplier for documentation if your customer or the destination country may want it.
Shelf Life and Re-Treatment Requirements
A common question is whether heat treatment expires. ISPM 15 does not set an expiration date for the mark, provided it is legible and the pallet has not been repaired with untreated wood.
In practice, older or faded marks can draw extra scrutiny at some destinations. Check the condition of the marks before loading, and check current regulations for the country you are shipping to.
Repairs matter. If a treated pallet is repaired with wood that has not itself been treated, the pallet is no longer compliant until it is treated and marked again. Ask how your supplier handles repaired pallets before ordering for export.
Heat Treatment vs. Chemical Treatment
Methyl bromide fumigation was once the main treatment method. It kills insects quickly but depletes the ozone layer and is hazardous to people, and the Montreal Protocol drove a shift away from it.
Pressure treatment with wood preservatives is sometimes confused with phytosanitary treatment. Pressure-treated wood is not ISPM 15 compliant on its own; it protects wood against decay over time but does not meet the standard's treatment requirements.
Heat treatment uses no chemical pesticide, which is one reason it is the most common choice.
Heat Treatment for Domestic Applications
ISPM 15 is an international trade standard, but some domestic buyers also ask for heat-treated pallets, for example where pest control and sanitation are priorities.
Some areas of the United States have quarantines on the movement of certain wood materials to limit specific pests. Check current regulations for the states you ship to and confirm requirements with your logistics partners.
If you have a food safety or customer audit program, check its current requirements for pallets. Some customers specify heat-treated pallets as part of their facility standards.
Sourcing Heat-Treated Pallets in Colorado
Heat-treated pallets are available in new and recycled form. Treatment adds to the cost; pricing comes by quote. Recycled heat-treated pallets need a check that the marks are intact and that no untreated boards were added during repair.
Pallet Colorado does not run a kiln or treat pallets. We connect you with partner suppliers in our network that offer heat-treated pallets in common sizes, including 48x40. Ask the partner supplier for documentation with your order and check the marks before loading.
If you export regularly, tell us your sizes and typical volumes in your quote request so the partner supplier can plan. Availability depends on partner suppliers.
About the Author
Pallet Colorado
Pallet Colorado is a referral service that connects Colorado businesses with partner pallet suppliers. We write practical guides on buying, selling, reusing and recycling pallets.
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