This document provides a drying chamber method for the determination of the dry matter content of paper, board, pulp and solid cellulosic nanomaterials, all of which can be produced from virgin and / or recycled materials. It is also applicable to the determination of the dry matter content of recycled paper and board. The procedure is applicable to paper, cardboard and pulp and cellulosic nanomaterials that do not contain a significant amount of volatile material at 105 ° C ± 2 ° C, other than water. Applicable, for example, to pulp, paper and board samples and cellulosic nanomaterials taken for chemical and physical testing in a laboratory where simultaneous determination of the dry matter content is required. This method is not applicable to the determination of the dry matter content of the pulp slurry nor to the determination of the commercial weight of the pulp batch. NOTE 1 ISO 638-2  specifies a chamber dryer method for determining the dry substance content in cellulosic suspensions of nanomaterials, ISO 287  provides the determination of the moisture content of a batch of paper and cardboard; ISO 4119  gives the determination of the pulp concentration; ISO 801 (all parts)  gives the indication of the commercial weight in lots. NOTE 2 This document specifies the total dry matter content of a sample, including any dissolved solids. If only a cellulosic material free of dissolved solids is desired, the dissolved solids are removed prior to measuring the dry solids content, e.g. by washing or dialysis, taking care to retain all cellulosic material; in cases where the sample can be filtered without loss of cellulosic solids, ISO 4119  can be used to determine the consistency of the pulp (solid cellulosic material content).