【国外标准】 Standard Test Methods for Air Permeability of Asbestos Fibers (Withdrawn 2022)

4.1 The degree of fiberization or subdivision of the asbestos fiber bundles in a specimen is related to its resistance to air flow. The number and size of the pores in the specimen are a function of the size of the fiber bundles and determine the resistance to air flow through the plug. Test specimens that have undergone a higher degree of fiberization will yield higher results provided the specimens compared are of similar specific gravities and other properties are not markedly different.4.2 These test methods are suitable for specification acceptance, manufacturing control, development, and applied research.4.3 It must not be assumed that all test specimens with equal test results have undergone equivalent degrees of fiberization. Some types of asbestos fiberize more readily than others. Particle size distribution and harshness can also influence permeability.1.1 These test methods cover the measurement of the relative degree of openness or degree of fiberization of milled asbestos fiber by air permeability instruments.1.2 Method A is the recommended procedure and describes a determination by means of the Rapid Surface Area apparatus. This test method is limited to fibers with an effective surface area in the range from 10 to 250 dm2/g [490 to 12 000 ft2 /lb].1.3 Method B is an alternative procedure and covers the use of the Dyckerhoff apparatus. This test method is limited to fibers within the range from 10 to 600 Dyckerhoff seconds.1.4 Only those asbestos specimens which are of similar specific gravities will bear strict comparison by these air permeability methods since differences in density result in specimens being tested under different conditions of porosity.1.5 Samples containing excessive quantities of nonfibrous particles or contaminants will not give reliable or meaningful results.1.6 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.1.7 Warning—Breathing of asbestos dust is hazardous. Asbestos and asbestos products present demonstrated health risks for users and for those with whom they come into contact. In addition to other precautions, when working with asbestos-cement products, minimize the dust that results. For information on the safe use of chrysotile asbestos, refer to “Safe Use of Chrysotile: A Manual on Preventive and Control Measures.”21.8 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.1.9 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.