This International Standard specifies a method for the determination of content of heavy extraneous materials larger than 3,15 mm by the use of sink-and-float separation combined with elutriation. This International Standard is applicable to woody biomass in accordance with ISO 17225-1, Table 1. NOTE 1 This method is designed to determine the level of impurities larger than 3,15 mm top size with a specific density > 1 g/cm³ such as stones, glass, rubber, metal and certain types of plastics. NOTE 2 During the processing of the sample hand sorting of light impurities with a specific density > 1 g/cm³ (e.g. plastic foil) may also be done.