Technical Guide: The HT Seal on Wooden Packaging, Pallets and Crates: Compliance or Quality?

For companies in the global manufacturing sector or any organization with export operations, selecting wood packaging is not just a cost decision, but one with profound strategic, legal, and operational implications. In this context, the heat treatment of wood packaging is vital both for protecting ecosystems and ensuring the continuity of international operations.

However, despite the common use of the HT Seal in export processes, a technical misconception exists that generates millions in losses: confusing phytosanitary compliance with the intrinsic quality of the material.

This document analyzes the legal foundations of NOM-144-SEMARNAT-2017 and ISPM-15, and explains why compliance with the standard alone does not guarantee efficient wood packaging.

1. The Legal Framework: ISPM-15 and NOM-144

It is essential to understand that heat treatment is a strictly phytosanitary protocol and not a manufacturing or industrial quality standard. While regulations require the elimination of pests to protect ecosystems, they do not affect or guarantee the physical properties, mechanical resistance, or degree of dryness of wooden pallets.

El sello certifica que la madera es segura para el medio ambiente, pero no asegura que sea la adecuada para soportar su carga, garantizar su vida útil o resistir la manipulación logística.

A. The International Standard: ISPM-15 (IPPC)

ISPM-15 recognizes specific methods for sterilizing wooden packaging [1]:

Heat Treatment (HT): Reach 56 °C at the center of the wood for 30 minutes.

Dielectric Heating (DH): Reach 60 °C for 1 minute. This is the recommended technology for a high-precision server crate due to its uniform heating.

B. The Standard in Mexico: NOM-144-SEMARNAT-2017

In Mexico, NOM-144 regulates the application of the mark. A common misconception is that the seal confers "quality" on the wood; in reality, it only provides the phytosanitary certification necessary for crossing borders [2].

2. The "Myth" of Drying in HT Treatment

Unlike the Kiln Dried (KD) process, the HT cycle is too short to significantly alter moisture content. As we explain in our technical guide on the importance of moisture content in wood, the water trapped within the fibers defines structural integrity and weight.

Dramatization: Even with the HT Seal, wood can still have high levels of moisture, depending on the treatment and storage conditions.

Technical Comparison: HT vs. K.D.

Factor	Heat Treatment (HT)	Oven Drying (KD)
Time on Camera	4 to 8 hours (average).	3 to 15 days (depending on the species).
Moisture Loss	1% to 3% maximum.	15% to 30% or more.

The Reality of Green Wood: If a supplier uses wood with 40% moisture content (green wood), after the HT certification process, you will receive wood packaging with 37% moisture. This is still unstable, heavy, and prone to deterioration.

Impact on Server Crates and Heavy Logistics

Overweight: A "green" pallet with the HT seal weighs up to 40% more, directly increasing export freight costs.

Instability: The wood will shrink during transit as it naturally loses moisture, which loosens the nails and compromises the rigidity of a server crate.

3. Anatomy of the Seal and Traceability: How to Audit the Mark on Your Wooden Packaging?

The seal is the packaging's "fingerprint." According to NOM-144, it must be legible, permanent, and placed on at least two opposite sides of the unit. For a company, validating each component is the first step in a compliance audit [2].

Component	Meaning	Audit Function
IPPC symbol	Convention Logo	It certifies compliance with the international standard.
MX	Country Code	Identify the origin of the treatment (Mexico).
000 (###)	Registration Number	Unique identification granted by SEMARNAT to the supplier.
HT / DH	Treatment Code	HT (Conventional Heat) or DH (Dielectric).

Critical point: The treatment code must exactly match what is stated on your certificate. If your server crate was processed using dielectric technology, the seal must say DH. Any inconsistency will result in customs rejection.

4. Why the HT Seal Doesn't Stop Mold

It's a scientific and regulatory fact: Mold is not a quarantine pest. According to the IPPC glossary of phytosanitary terms (ISPM 5), a quarantine pest is one of potential economic importance to the endangered area where it is not yet present [4]. Common mold fungi (Aspergillus, Penicillium) are ubiquitous and cosmopolitan organisms; that is, wood mold lives everywhere.

Since it is not an "invasive" threat to foreign forests, customs authorities do not target it with the HT seal, which only guarantees that wooden pallets do not transport destructive insects (wood-boring pests) [1][3].

1. Zero Residual Effect: The HT sterilizes the wood immediately, but does not protect it against new environmental spores.

2. The 20% Threshold: Fungi generally require a moisture content (MC) above 20% to grow [3]; as a widely accepted rule of thumb in wood engineering, maintaining the MC at or below 20% significantly reduces the risk of biodeterioration.

   As we detail in our article on what it means for wood to be "dry," biological stability depends on actual drying, not on a sound seal.

   
   

5. Purchasing and Quality Audit Checklist

To ensure your wooden packaging is functional and not just "legal," your inspection should include:

1. Require Thermal Recording: Verify the official chart showing 56°C for 30 minutes for the specific batch of your wooden pallets.

2. Measure the Humidity Level Upon Receipt: If your hygrometer reads >19%, you have green wood. It has the legal certification, but it lacks the necessary industrial quality.

3. Prevent Re-humidification: Follow good storage practices (elevation and ventilation) to prevent ambient humidity from compromising the material's hygiene.

Conclusion

The HT seal represents the minimum legal compliance, but kiln-dried (KD) wood is the engineering standard. A strategic partner like Kayak Packaging ensures that its wooden packaging, wooden pallets, and every server crate meet NOM-144 standards without sacrificing physical integrity or increasing logistics costs due to excess moisture.

References:

1. IPPC (2018). ISPM 15: Regulation of wood packaging used in international trade. FAO.

2. SEMARNAT (2017). NOM-144-SEMARNAT-2017. Official Gazette of the Federation.

3. Forest Products Laboratory (USDA). Wood Handbook. Chapters 13 and 14.

4. IPPC (2021). ISPM 5: Glossary of Phytosanitary Terms.