We have run an ISPM-15 registered chamber since 2018. It is an unglamorous piece of equipment that does one thing precisely, and the precision is the entire point.
Here is what a cycle actually involves, because a surprising number of people buying heat-treated pallets have no picture of what they are paying for.
The requirement
ISPM-15 specifies a minimum core temperature of 56 °C sustained for at least 30 continuous minutes throughout the profile of the wood. Not surface temperature. Not average temperature. Core, everywhere in the load.
That last word does the work. A chamber can be at 70 °C for two hours while the middle of a tightly stacked pallet in the centre of the load is still at 40 °C. The standard is about the coldest piece of wood in the chamber, and everything about how a cycle is run follows from that.
Probe placement is the whole job
Temperature probes are drilled into the wood — not laid on the surface — in the locations expected to heat last. In practice that means the centre of the load, in the thickest member, usually a stringer rather than a deck board.
Get the probe placement wrong and you will produce a beautiful chart showing a compliant cycle for wood that never reached temperature. This is where compliance is genuinely won or lost, and it is why registration involves someone qualified verifying the loading pattern rather than just the equipment.
We run a fixed loading pattern for exactly this reason. Non-standard loads get a fresh probe placement decision and a longer cycle, and we charge accordingly, because the alternative is guessing.
| Stage | Typical duration | What is happening |
|---|---|---|
| Load and probe | 20–30 min | Fixed stacking pattern, probes drilled into the coldest members |
| Ramp | 90–150 min | Chamber to temperature; core lags substantially |
| Hold | 30 min minimum | Core at or above 56 °C, continuously, everywhere |
| Cool and unload | 45–60 min | Chart printed and filed; marking applied |
| Total | ≈ 3.5–4.5 hours | Per chamber load |
What it does to the wood
It kills insects and larvae, which is the point. It also drives off moisture — a pallet typically comes out of a cycle two to four percentage points drier than it went in, which is a genuine benefit for anything going into a container for six weeks.
It does not meaningfully weaken the wood at these temperatures. There is a mild darkening, sometimes some surface checking on wood that was wet to start with, and occasionally resin bleed on softwood. None of it is structural.
It is also not the same as kiln drying, which is a moisture process with different parameters. A KD stamp is not an ISPM-15 mark and will not clear customs, and the confusion between the two is one of the more expensive misunderstandings in export.
Marking, and the part people get wrong
After a compliant cycle, the mark goes on: IPPC wheat symbol, country code, our facility registration number, and the treatment code HT. On at least two opposing sides, stencilled or branded, permanently.
The part people get wrong is afterwards. A compliant marked pallet repaired with untreated lumber is no longer compliant, and it still carries the mark. That is the single most common ISPM-15 failure we see, and it is invisible unless someone is tracking treatment through the repair process.
We segregate treated stock and repair it only with treated lumber, then re-mark. Ask your repair yard whether they do the same. If the answer is not immediate, your compliance chain has a hole in it.