What "heat treated" does — and does not — sterilise
In short
ISPM-15 heat treatment raises the wood core to 56°C for thirty continuous minutes. That is a phytosanitary measure aimed at wood-boring insects and their larvae. It is not sterilisation, it does not address bacteria or mould in any lasting way, and a pallet can be re-contaminated the moment it leaves the chamber. Asking for HT stock for hygiene reasons buys you a stamp, not a clean pallet.
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What the treatment actually does
The wood core is raised to a minimum of 56 degrees Celsius and held there for at least thirty continuous minutes. Probes are set in the thickest members of the load, because the standard is about the temperature of the wood rather than the temperature of the air around it — a distinction that is the difference between compliance and an under-treated load that passes a chamber log and fails an inspector.
The target is wood-boring insects and their larvae: the pests that move between countries inside packaging and establish themselves in forests that have no defences against them. That is the entire purpose of ISPM-15, and by that measure the treatment works well.
What it is not
| Concern | Does HT address it? | What actually does |
|---|---|---|
| Wood-boring insects and larvae | Yes — this is the purpose | HT, DH or fumigation |
| Surface bacteria | Temporarily, at best | Non-porous surface, or sealed packaging between product and pallet |
| Mould | Kills existing growth; does not prevent return | Moisture control below 19% |
| Chemical residue from previous freight | No | Segregated clean-core line, provenance control |
| Odour | Partially | Source control and segregation |
| Future re-infestation | No — treatment is a moment, not a state | Dry storage, fast rotation, clean handling |
What to ask for instead
If your concern is genuinely hygiene rather than phytosanitary compliance, the useful specification is about provenance and condition, not about a chamber cycle.
- A dedicated clean-core line with no agricultural or chemical returns in the stock
- Moisture content below 19%, verified, with no mould bloom on any surface
- No staining, residue or odour — with rejection criteria written down rather than implied
- Dry, covered storage at your own site, because a clean pallet on a wet dock stops being one quickly
- Fast rotation, which beats every treatment available
And if your concern is export, then yes — you need HT, you need the IPPC mark on at least two opposite sides, and you need the treatment record on file. Just do not expect the two requirements to be the same requirement, because they are not.
Appendix: the data behind this
Every piece on this site closes with the slice of our operating record that bears on what it argues. The full record is published at /resources/operating-record.
Observed kiln cycle times
These are heat cycles, nothing more. The variation is entirely about how long it takes a given species and section to reach 56°C at the core.
| Species | Section | Starting MC | Typical cycle | Note |
|---|---|---|---|---|
| Yellow poplar | 1.5 in stringer | 14% | 4.5 – 5.5 hrs | Fastest common stringer stock we treat. |
| Southern yellow pine | 1.5 in stringer | 15% | 5.0 – 6.5 hrs | Resin can extend hold time in a heavily loaded chamber. |
| Red oak | 1.5 in stringer | 16% | 6.5 – 8.5 hrs | Dense and slow. The species that sets our scheduling. |
| Hard maple | 1.5 in stringer | 15% | 7.0 – 9.0 hrs | Longest routine cycle on our board. |
| Mixed hardwood | 3.5 in block | 17% | 8.5 – 10.5 hrs | Block pallets probe in the block, never the deck. |
| Any | Above 19% MC | 20%+ | +2.0 – 3.5 hrs | Wet stock costs kiln hours. This is why we ship dry. |