Working Party 2.5 of the IRG was set up in 1995 in response to discussion around proposals for an International Wood Preservation Standard. Two years later, ISO Technical Committee 165 Timber Structures set up a subcommittee SC1 Wood Materials – Durability and Preservation to address this issue. It was agreed that neither the European Hazard Class system nor any other regional system could be implemented worldwide without modification. A compromise system was developed that could be applied worldwide though not all hazards might be present in all regions. There are five major classes each of which has subdivisions. In some cases the subdivisions are based on the degree of exposure to moisture, in other cases they are based on the presence or absence of specific types of organisms with different levels of aggressiveness towards treated wood. If adopted widely, the international Use Classification system should assist in reducing the potential for confusion for international trade in treated wood products.

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