This part of ISO 17225 determines the fuel quality classes and specifications of graded wood chips. This part of ISO 17225 covers only wood chips 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. This standard covers only wood chips, which are produced with sharp tools, and does not cover hog fuel, which is produced with blunt tools.