【国外标准】 Standard Test Methods for Direct Moisture Content Measurement of Wood and Wood-Based Materials

4.1 Moisture content is one of the most important variables affecting the properties of wood and wood-based materials. The procedures in these test methods are structured to permit the full range of use from fundamental research to industrial processing. Method A is the reference (primary) standard for determining moisture content of wood and wood-based materials, which is designed for obtaining the most precise values of moisture content consistent with the needs of the user. It provides means of assessing variability contributed by the oven or specimen hygroscopicity, or both. In addition, criteria are described for defining the endpoint in oven-drying. Method B provides relatively simple procedures of measuring moisture content, but generally with a lower precision than Method A. Representativeness of the specimens to the full-size product, including knots, sapwood, and heartwood, needs to be considered. These methods are not recommended for use with treated wood products impregnated with creosote, petroleum, and their solutions where the volatile non-wood chemicals contained in the specimen introduce greater bias than desired in the results.1.1 These test methods cover the determination of the moisture content (MC) of wood, veneer, and other wood-based materials, including those that contain adhesives and chemical additives. The test procedures appear in the following order:    Sections  Method A—Primary Oven-Drying Method 5  Method B—Secondary Oven-Drying Method 61.2 The primary oven-drying method (Method A) is intended as the sole primary method. It is structured for purposes where the highest accuracy or degree of precision is needed (for example, research or calibration).1.3 The secondary oven-drying method (Method B) is intended for the purposes where the primary procedure (Method A) is not desired or justified. Test results in this method are generally less precise than in Method A.1.4 For materials that have been chemically treated or impregnated with creosote, petroleum, and their solutions such that the oven-drying procedures introduce greater bias than desired in the results, other methods, such as AWPA A6, are recommended.1.5 Units—The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.