Dielectric heating (DH)
Also called: DH, microwave treatment, radio frequency heating
Dielectric heating (DH) is an ISPM 15 treatment that heats wood packaging with microwaves or radio waves until the entire profile of the wood, including its surface, reaches at least 60 °C for 1 continuous minute. Treated wood is marked with the code DH.
In depth: ISPM 15: the wood packaging standard for international shipping
DH is a heat treatment, but ISPM 15 gives it its own code and parameters because the heat comes from inside the wood rather than from hot air.
DH vs HT
| Parameter | DH | HT |
|---|---|---|
| Energy source | Microwaves or radio waves | Steam or hot-air chamber |
| Temperature | At least 60 °C | At least 56 °C |
| Duration | 1 continuous minute | 30 continuous minutes |
| Coldest point | Usually the surface | Usually the core |
| Mark code | DH | HT |
ISPM 15 notes that for wood thicker than 5 cm, heating at 2.45 GHz needs bidirectional application or multiple waveguides to heat evenly. Treatment providers must verify their schedules against moisture content, size, density and frequency, and schedules should be approved by the NPPO.
Why it matters
DH treats wood fast, which suits continuous conveyor processing. It is much less common for pallets than conventional HT, so availability varies by region.
On a spec sheet or RFQ
Most buyers specify "ISPM 15 HT". If you will accept DH, write "ISPM 15, HT or DH". Importing countries that follow ISPM 15 should accept both codes.
Common confusions
DH is not "kiln drying". Its target is a short, even pest-killing temperature, not a moisture content. A DH-marked pallet can still be wet.
Related
- GlossaryWhat is heat treatment (HT) for pallets?Heat treatment (HT) is the ISPM 15 method of heating wood packaging until the whole profile of the wood, including its core, reaches at least 56 °C for 30 continuous minutes. Treated pallets carry the IPPC mark with the code HT.
- GlossaryWhat is ISPM 15?ISPM 15 is the International Plant Protection Convention (IPPC) standard for wood packaging material in international trade. It requires pallets, crates and dunnage made of solid wood to be debarked, treated by an approved method such as heat treatment (56 °C core for 30 minutes), and marked with the IPPC mark.
- GlossaryIPPC markThe IPPC mark is the stamp that shows wood packaging was treated under ISPM 15. It contains the IPPC symbol, a two-letter ISO country code, a producer or treatment provider code assigned by the national plant protection organization, and a treatment code (HT, DH, MB or SF), inside a border.
- StandardsISPM 15: the wood packaging standard for international shippingISPM 15 is the IPPC standard requiring solid-wood packaging, including pallets and dunnage, to be debarked, treated (HT, DH, MB or SF) and marked before crossing a border. Plywood, OSB, presswood, wood 6 mm thick or less, and plastic, metal and paper pallets are exempt.
- GuidesHeat-treated pallets (HT): what they are, when you need them, and costA heat-treated (HT) pallet's wood core was held at 56 °C (133 °F) for 30 minutes under ISPM 15, then stamped with the IPPC mark and HT. Most countries require it on wood pallets crossing their border. It adds roughly $1–3 per pallet (2026 US estimate) and kills pests; it does not dry the wood.
More in Standards and compliance
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- GlossaryFSMA (Food Safety Modernization Act)FSMA is the US Food Safety Modernization Act of 2011. Under its Sanitary Transportation of Human and Animal Food rule (21 CFR Part 1, Subpart O), pallets are transportation equipment and must be designed and maintained so they are suitable and adequately cleanable, and do not make food unsafe.
- GlossaryGMAGMA stands for the Grocery Manufacturers Association (now the Consumer Brands Association), whose name became attached to the standard 48 × 40 in (1219 × 1016 mm) US grocery pallet: a partial four-way wood stringer pallet with three notched stringers, seven top and five bottom deckboards.
- GlossaryGS1GS1 is a global, not-for-profit standards organization that issues company prefixes and maintains the identification and barcode standards used in supply chains, including GTINs for products, the SSCC for logistics units such as pallets, and the GS1-128 barcode.
Last reviewed 2026-09-24. 231 words.