Two paths to the same stamp
Under ISPM-15, a pallet can earn its compliant mark by either killing pests with heat or gassing them with a fumigant. Heat treatment raises the wood core to at least 56 degrees Celsius for 30 continuous minutes, while methyl bromide fumigation seals the wood in a chamber or under tarps and introduces the gas at a controlled dosage. Both produce a pallet that inspectors will accept, but the mark hides meaningful differences in cost, safety, and market access.
The treatment code in the IPPC mark tells the reader which method was used, HT for heat treatment and MB for methyl bromide. That single code increasingly influences whether a shipment sails smoothly, because a growing list of countries prefers or requires the HT designation. Choosing a method is therefore not just an operational decision but a market-access decision that shapes where your goods can go.
How heat treatment works
Heat treatment is a kiln process. Pallets go into a chamber where hot air, and sometimes steam, drives the internal wood temperature to the required threshold and holds it, with probes verifying the core reaches temperature rather than just the surface. The physics are straightforward: sustained heat denatures the proteins of insects and larvae throughout the board, so nothing living survives the cycle.
A useful side effect is drying. Because the process drives off moisture, heat-treated pallets tend to be lighter and less prone to mold in transit, which matters for long ocean voyages. The equipment investment is real, but once a kiln is running, the marginal cost per pallet is low and the output is a clean, residue-free, market-ready export unit that needs no ventilation or handling precautions afterward.
How fumigation works, and why it is fading
Fumigation kills pests chemically rather than thermally, which is why it can treat wood that is too thick or too wet to heat efficiently. That flexibility was once its main advantage. But methyl bromide is a potent ozone-depleting substance controlled under the Montreal Protocol, and it is acutely toxic to the workers who apply it, requiring careful containment, monitoring, and aeration before the wood can be handled.
Those liabilities have driven a steady global retreat from fumigation. The European Union and a number of other jurisdictions have effectively barred methyl bromide fumigated wood packaging, and even where it is legal, the handling burden and environmental scrutiny make it unattractive. A pallet marked MB now faces a shrinking set of acceptable destinations, which turns the method into a strategic dead end for most exporters.
Residue, safety, and food-adjacent cargo
For any cargo near food, pharmaceuticals, or consumer goods, the residue question settles the debate. Heat treatment leaves nothing behind but drier wood, so there is no chemical to migrate into sensitive product. Fumigation, even after aeration, carries the perception and sometimes the reality of residual chemical, which many quality-conscious buyers simply will not accept on their packaging.
Worker safety points the same direction. A kiln operator manages heat and equipment; a fumigation crew manages a toxic gas with strict exposure limits. The lower risk profile of heat treatment reduces liability, insurance friction, and regulatory oversight for the operator. When you weigh the total burden rather than just the treatment fee, heat treatment usually comes out cleaner on nearly every axis that matters.
Cost and throughput realities
On paper, fumigation can look cheaper per cycle because it needs less capital than a kiln, but the full accounting rarely favors it. Chemical cost, licensed applicators, monitoring, aeration time, and disposal of scrutiny add up, and the market-access penalty is a hidden cost that can strand inventory. Heat treatment front-loads capital into a kiln but then runs cheaply and predictably at volume.
Throughput also favors a well-sized kiln for a steady export operation. A kiln can cycle batches continuously, and once amortized, delivers a low and stable per-pallet cost. Fumigation is better suited to occasional or specialized needs where heating is impractical. For a company shipping export pallets routinely, investing in or sourcing from heat treatment capacity is the economically and strategically sounder path.
Making the call for your lanes
The decision comes down to where you ship and what you ship. If your goods move to Europe, Australia, or other jurisdictions that restrict methyl bromide, heat treatment is effectively mandatory. If you handle food-adjacent or high-value cargo, the residue-free profile of heat treatment protects both your product and your customer relationships, which usually outweighs any per-cycle cost difference.
The practical recommendation for most US exporters is to standardize on heat-treated, properly marked pallets and reserve fumigation only for the rare case where a specific destination or cargo demands it. Standardizing avoids the risk of accidentally shipping an MB-marked pallet into a country that refuses it, and it simplifies the yard by keeping one compliant export stock rather than two.
Key takeaways
- Both methods satisfy ISPM-15, but the mark carries an HT or MB code that increasingly determines market access.
- Heat treatment drives the wood core to 56 degrees Celsius for 30 minutes and leaves no residue.
- Methyl bromide is an ozone-depleting, toxic gas being restricted or banned in the EU and elsewhere.
- Heat treatment is the clear choice for food-adjacent cargo and for worker safety and lower liability.
- Standardizing on heat-treated export stock avoids shipping an MB pallet into a country that refuses it.
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