Guide: heat treatment
ISPM 15 and heat-treated pallets, explained
ISPM 15 is the international standard that regulates wood packaging material in international trade. For pallets, it means the wood has been heat treated so its core reached at least 56 °C for at least 30 minutes, and marked.
What the rule asks
Wood packaging materials must be debarked before heat treatment or fumigation. Allowed bark on debarked wood may be less than 3 cm wide, or if wider than 3 cm, its surface area must be under 50 square cm. Two treatments are approved: heat treatment (HT) and methyl bromide fumigation (MB). Pallets for export in this trade are heat treated.
Heat treatment, defined
| Measure | Requirement |
|---|---|
| Core temperature | At least 56 °C (133 °F) |
| Time at that temperature | At least 30 minutes |
| Prior step | Debarked |
Where the rule applies
It depends on the destination. A pallet shipped inside Florida needs no mark. A pallet headed across a border that follows ISPM 15 does. Each importing country sets its own requirement through its plant protection agency, so ask the receiver before ordering.
What it does not cover
- Dryness. A heat-treated pallet can be wet.
- Mould. Pallets loaded into trailers while still hot are susceptible to mould; heat treatment does not make wood immune.
- Grade. Treatment is separate from repairs.
Asking for treated stock
Say that the pallets must be heat treated and where they are going. The heat-treated pallets page has the ordering side. The rule is explained here; certification and stamping are separate, and the mark on the pallet you receive is what counts.
Questions, answered
Do I need heat-treated pallets for export?
If the destination applies ISPM 15 to wood packaging, yes. Check the receiver and the rules of the country.
Is heat treatment the same as kiln drying?
Not quite. Kiln drying is listed as one of the ways to reach the temperature, but heat treatment is defined by the core temperature and time, not by the wood being dry.
What the mark records
The mark contains the IPPC symbol, a two-letter country code, the number of the producer, the agency that supervises the facility and the treatment code. In the United States, APHIS says producers label heat-treated packaging with the quality mark of an agency accredited by the American Lumber Standard Committee. HT means heat treatment, MB methyl bromide fumigation, and DUN marks dunnage, the loose timbers used to brace a load, which is not applied to a manufactured pallet.
Two points to remember
- Importing countries set and revise their own wood-packaging rules, so the receiver is the one to ask.
- Treatment is verified by the producer's agency, not by the buyer: a buyer checks the mark.
How the rule spread
The Wikipedia article on ISPM 15 records that New Zealand was the earliest country in its table to adopt the standard, in April 2003, and gives September 2005 for the United States. A 2009 revision brought in the European Union's limits on bark, and Australia applied those limits from 1 July 2010. The article lists around fifty entries, with the EU counted once for its 27 members, and advises checking the export authority for current requirements, which is the sensible reading for any exporter.
Bark limits, in numbers
After debarking, small pieces of bark are allowed if each is narrower than 3 centimetres, whatever its length. A piece wider than 3 centimetres is allowed only when its surface area is under 50 square centimetres. A pallet with a strip of bark on a stringer that is wider than a hand-width or longer than a thumbnail is a pallet an inspector may question.
Sources
Last reviewed 10 November 2026.