This part of ISO 17225 determines the fuel quality classes and specifications of graded wood briquettes. This part of ISO 17225 covers only wood briquettes produced from the following raw materials (see ISO 17225-1, Table 1): 1.1 Forest, plantation and other virgin wood 1.2 By-products and residues from wood processing industry 1.3.1 Chemically untreated used wood NOTE Thermally treated biomass briquettes (e.g. torrefied briquettes) are not included in the scope of this part of ISO 17225. Torrefaction is a mild pre-treatment of biomass at a temperature between 200 300 °C.