ISPM15 and treatment
Heat treatment and what HT means
HT is the treatment code you will see most often on UK export pallets. It is also the element most often confused with kiln drying, which is a different process carried out for a different reason.
What heat treatment is for
Solid softwood can host insect larvae, beetles and fungal organisms deep inside the timber. The purpose of heat treatment under ISPM15 is to raise the temperature throughout the wood, including its core, for long enough to kill those organisms. The target is the profile of temperature and time reached inside the timber — not the temperature of the chamber and not the appearance of the finished board.
What it involves in practice
A registered operator treats the wood in a chamber or kiln that is monitored and controlled, records the treatment, and applies the mark to the packaging it has treated. The elements that matter operationally are:
- Core temperature, not surface temperature. Probes are placed to measure the coldest point in the load, because that is the point that determines whether the treatment worked.
- A held duration. The specified temperature has to be maintained for a continuous specified period, not merely touched.
- Records. Treatment is logged, and the operator’s registration depends on those records standing up to inspection.
- Marking. Only the operator registered to do so applies the mark, and it applies it to what it actually treated.
The specific temperature and duration parameters, and the alternative dielectric heating measure abbreviated DH, are set out in the standard itself. Where a number matters to your contract or your customer’s specification, take it from the published standard rather than from a supplier’s summary — including ours.
Kiln drying is not heat treatment
Why the confusion is expensive
The two processes sound similar, both involve kilns, and suppliers outside the export trade often use the terms loosely. An exporter who buys “kiln-dried pallets” in good faith, believing the treatment question is handled, can find at the point of loading that the pallets carry no mark at all. By then the load is built and the collection is booked.
The test is simple and it is physical: where treated wood packaging is required, look for the mark on the wood. If it is not there, the treatment question is not answered, whatever the paperwork says.
Does treatment expire?
No. There is no re-treatment interval built into the standard, and a correctly treated and marked pallet does not become untreated with age. What changes with age is the condition of the pallet and the legibility of the mark, and what changes with repair is which components the mark can honestly be said to cover — see repaired and remanufactured pallets.
Heat treatment and the goods on the pallet
Heat treatment is a plant-health measure applied to the wood. It is not a hygiene certification, not a sterilisation of the pallet surface, and not a food-contact approval. If your goods need pallets that are clean, dry and free of staining, that is a separate specification to state when you enquire, and it is one we can work to.
Related guides
How to read an ISPM15 stamp
Every element of the mark explained, plus the practical signs that a mark should not be relied on.
When ISPM15 applies — and when it does not
Which goods, materials and destinations bring the standard into play. An expensive thing to get wrong in either direction.
Export documentation for palletised freight
The paperwork that travels with a palletised consignment, and where the pallet itself appears in it.
Tell us where it's going and we'll help you choose
Send your destination, pallet size, quantity and deadline, or upload photographs of the pallets and marks you already have. A person reads every enquiry.