Guide: the stamp
How to tell if a pallet is heat treated
A heat-treated pallet carries the ISPM 15 mark, a stamp or brand with the IPPC symbol, a country code, a certification number and the letters HT.
Read the mark
| Part | What it is |
|---|---|
| IPPC symbol | The certification symbol that shows the mark is under the international convention |
| Country code | A two-letter ISO country code; the United States is US |
| Certification numbers | The regulating agency and the treatment provider or manufacturer |
| Treatment code | HT for heat treatment, or MB for methyl bromide |
Where to look
On the side of a deck board, stringer or block, burned or stamped into the wood. A pallet that went through treatment should show it; one that did not will not. If the mark is smudged beyond reading, treat the pallet as unmarked.
What you cannot tell from a mark
- Whether it has dried since. A treated pallet can be wet.
- Whether it is clean of mould.
- What grade it is; stamp and grade are separate.
- Whether the stamp is genuine. Check the supplier for that.
If it is not there
A pallet without the mark can still be sound, just not usable for export freight that needs it. Stamped stock can be ordered with the size and build; see heat-treated pallets.
A worked example of a mark
A well-formed American mark reads from left to right: the IPPC symbol, then US, then a number for the producer and the letters of the accredited agency, then HT. A mark missing the agency or the country, or one with a treatment code that is not HT or MB, is not a compliant mark. The letters KD, which stand for kiln dried, may appear next to HT; they describe a moisture standard in addition to the heat treatment.
Where an inspector looks
- On a stringer or block, because boards are sometimes swapped after treatment.
- On two opposite sides, as the standard asks, so one view of the pallet is enough.
- For boards of a different colour from the rest: a replacement board has no mark of its own.
A quick decision tree
- Find the mark. No mark means untreated, whatever the seller says.
- Check for the symbol, the country code and a treatment code.
- Read the treatment code. HT is heat treatment; MB is methyl bromide.
- Look for mixed boards. A board without any mark was fitted later.
- Check the moisture. The mark says nothing about dryness.
Checking a delivery against the order
Pull five pallets from different parts of a delivered stack and read the mark on each. Every one should show the same producer number and the same treatment code. A mix of marked and unmarked pallets in a load ordered as treated means the supplier has filled the order from more than one source, and the unmarked ones cannot go on the export freight. Keep a photograph of each mark with the delivery note.
Marks that look similar but are not ISPM marks
Pallets carry many stamps. A rental pool's name on a block, a company stencil on a deck board, a lumber grader's stamp and a brand showing a manufacturer's plant number can all sit near a treatment mark, and none of them proves treatment. The IPPC symbol, the country code and a treatment code together are what to look for. Euro pallets add the EUR and EPAL marks next to the ISPM mark, and those describe the pallet's build rather than its treatment.
Optional letters on a mark
The mark may include DB, for debarked, though it is assumed and usually left off. DUN may appear on loose dunnage wood used to brace a load. A country code shows where the pallet was treated, not where the freight began, so a pallet marked US can sit in an inbound container from anywhere. Photograph a mark in side light from a low angle if it is faint, since burned marks can be read when a flash flattens them.
Sources
Last reviewed 12 November 2026.