This document determines the fuel quality classes and specifications of graded hog fuel and wood chips for industrial use. It covers only hog fuel and 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 Used wood; — 1.4 Blends and mixtures. This document covers hog fuel that has pieces of varying size and shape, produced by crushing with blunt tools such as rollers, hammers, or flails, and wood chips which are defined as chipped woody biomass with a sub-rectangular shape and a typical length of 5 mm to 50 mm typically in the form of pieces with a defined particle size produced by mechanical treatment with sharp tools such as knives. See 1.1.2 in ISO 17225-1, Table 1 for by-products and residues from wood processing industry, which can include chemically treated material (e.g. glued, painted, laminated), are not allowed to contain halogenated organic compounds or heavy metals at levels higher than those in typical virgin material values or higher than typical values of the country of origin (see Annex B in ISO 17225-1). NOTE If 1.4 Blends and mixtures includes 1.3.2 Chemically treated used wood, it can be only used in the installations permitted to use 1.3.2.