International Standards for Phytosanitary measures No. 15 according to Wikipedia on ISPM-15  is a standard and measure that was developed by the (IPPC) International Plant Protection Convention to directly address the concern and need to treat wood materials that ship between countries.

Approved phytosanitary measures significantly reduce the risk of pest spread and introduction through wood packaging material. Having the ISPM-15 mark or “wheat-stamp” ensures that all contents have been subjected to heat treatments for safe transportation and shipping.

By adhering to the ISPM-15 standards you save time and money with all of your shipping of applicable wood; wood packaging materials such as dunnage, crates, reels, collars, and pallets; and other wooden items such as bracing.

Shipping containers and packages that do not meet these standards at a receiving countries borders, port, or point of entry may be held up for weeks until they are properly scanned and processed.

The following articles are of sufficiently low risk to be exempted from the provisions of this standard

• Plastic
• Paper
• Metal
• Plywood
• Hardboard
• Oriented Strand Board or Veneer
• Thin wood 6mm or less in thickness
• Barrels for wine and spirits that have been heated during manufacture
• Gift boxes for wine, cigars, and commodities that have been processed
• Sawdust, Wood Shavings, and Wood Wool
• Wood components permanently attached to freight vehicles and containers

Source * Food and Agriculture Organization of the United Nations International Plant Protection Convention (IPCC) for the full .PDF Regulation of wood packaging material in international trade

HEAT TREATMENT

Various energy sources are suitable to meet the required treatment standards.

• Steam Heating
• Kiln-Drying
• Heat-enabled chemical pressure
• Dielectric Heating ( microwave, radio frequency )

This mark indicates that wood packaging material has been subjected to approved phytosanitary treatment in accordance with all standards and is composed of the following required components :

• The Symbol
• A Country Code
• A Producer / Treatment Provider Code
• A Treatment Code using the appropriate abbreviation ( HT, DH or MB).

Symbol

The design of the symbol must meet registered nation, regional, or international certification that closely resembles the examples shown to the left side of the other components.

Country Code

the country code must be the ISO or International Organization for Standards two-letter country code. It must be separated by a hyphen from the treatment/provider code.

Treatment code
The treatment code is an IPPC abbreviation as provided in Annex 1 for the approved measure used and shown in the examples as “YY”. The treatment code must appear after the combined country and producer/treatment provider codes. It must appear on a separate line from the country code and
producer/treatment provider code, or be separated by a hyphen if presented on the same line as the other
codes.

Treatment Code and Type

HT  – Heat treatment
MB – Methyl bromide
DH – Dielectric heating

These are examples of the IPCC and ISPM-15 stamp or mark that is used to certify that the wood packaging materials have been subjected to and approved of the heat treatment standards

The mark must be

1. Legible
2. Durable and non-transferable
3. Placed in a location that is visible when the wood packaging is in use, preferably on at least two opposite sides of the wood packaging unit.
4. Can not be hand drawn
5. Devoid or absent of red or orange as those colors are delegated for the labeling of dangerous goods.