Wooden pallets and crates can be easily inhabited by insects, or contaminated by bacteria which can damage the goods and affect those who consume them. This is especially hazardous when transporting food and medical products. Timber pests can spread diseases and damage the ecosystems in other countries.
ISPM-15 stipulates that any wood thicker than 6mm being transported across borders must be debarked, and stamped with a mark of compliance. This mark can only be achieved by heat treating the wood, or fumigating it using methyl bromide.
Methyl bromide is a toxic, corrosive substance, which is unsuitable for treating pallets used for food and pharmaceuticals. Therefore, heat treatment is widely preferred over fumigation.