Ship wood across a border and you enter the world of ISPM-15. Here's what the stamp means, how treatment actually works, and how to avoid a quarantine surprise.
Why Borders Care About Your Pallet
The pallet under your export shipment is not just packaging in the eyes of customs authorities; it is a potential vehicle for invasive pests. Raw wood can harbor insect larvae and fungi that, once released into a new ecosystem, can devastate native forests with no natural predators to keep them in check. Whole regions have lost tree species to pests that hitchhiked in untreated wood.
ISPM-15 is the international standard built to address exactly this risk. It governs wood packaging material used in global trade and requires that solid wood components be treated to neutralize pests before crossing many borders. The standard is administered through national plant protection organizations, but its logic is shared worldwide.
Understanding it is not optional for exporters. A non-compliant pallet can get an entire shipment refused, fumigated at the dock, or sent back, turning a paperwork detail into a very expensive delay.
The Stamp That Tells the Story
Compliant wood packaging carries a distinctive mark that customs officials are trained to read at a glance. The mark includes the international plant protection symbol, a country code, a unique number identifying the treatment provider, and a treatment code indicating which method was used. It is a small stamp carrying a lot of regulatory weight.
The two treatment codes you will encounter most are HT for heat treatment and MB for methyl bromide fumigation. Reading the stamp tells an inspector both that the wood was treated and how. A missing, illegible, or counterfeit mark is treated as no treatment at all, regardless of what was actually done to the wood.
Because the mark is the proof, its placement and legibility matter. It should be visible on at least two sides of the unit and must remain readable through the life of the pallet, which is one more reason to keep export pallets in good condition.
How Heat Treatment Works
Heat treatment, marked HT, neutralizes pests by cooking the wood. The standard requires that the core of the wood reach a specified minimum temperature and hold it for a sustained period. The point is to ensure the heat penetrates all the way through, not just the surface, so that anything living inside the board is killed.
The wood goes into a kiln or heat chamber where temperature is monitored to confirm the core actually reaches the target. This is a physical process with no chemical residue, which is a large part of why it has become the dominant and preferred method in most markets.
From a practical standpoint, heat-treated wood is clean, widely accepted, and free of the handling restrictions that come with chemical fumigants. For most exporters, HT is the path of least resistance and the safest default.
How Fumigation Works
Fumigation with methyl bromide, marked MB, neutralizes pests chemically by exposing the wood to a gas in a sealed environment for a set duration. Historically it was common, and it still appears, but its role has been shrinking for both environmental and health reasons.
Methyl bromide is an ozone-depleting substance, and its use has been restricted or phased out in many jurisdictions under international environmental agreements. Some destinations now actively discourage or refuse MB-treated wood, which makes it a riskier choice for exporters who want predictability across many lanes.
If you have a choice, heat treatment is almost always the smarter pick. Fumigation tends to make sense only in narrow cases where heat treatment is impractical and the destination still accepts the chemical method.
Common Compliance Mistakes
The most frequent error is assuming all wood components in a shipment are covered when one is not. Dunnage, blocking, bracing, and crating all count as wood packaging material and all need treatment and marking. A single untreated scrap of bracing can compromise an otherwise compliant load.
Another classic mistake is reusing a pallet that has been repaired with untreated wood. Once you add a non-compliant board, the whole unit's compliance is in question. Proper repair for export pallets means using treated material and, where required, re-marking appropriately.
A third pitfall is illegible or damaged marks. Even correctly treated wood can be rejected if an inspector cannot read the stamp. Treat the mark as part of the cargo's documentation and protect it accordingly.
A Pre-Export Checklist
Before a wood-packed shipment leaves, confirm that every wood component is treated and marked, not just the main pallet. Walk the load and look at dunnage and bracing specifically, since those are the pieces that get forgotten. Verify the marks are present, legible, and on visible faces.
Check the destination's current requirements, because acceptance of fumigation in particular can vary and change over time. What was acceptable on a lane last year may not be this year. A quick verification beats a quarantine.
When in doubt, source export pallets from a supplier who handles treatment and marking as part of the build and repair process. We supply and repair ISPM-15 compliant wood packaging, which keeps the responsibility for getting the stamp right where it belongs, on the people who do it every day.
Theo Brandt
Logistics, PalletsRecyclingUSA — Woods Cross, Utah.