This specification covers asbestos yarns having a specified minimum % mass of asbestos fiber, excluding the mass of other inorganic reinforcing strands which may be present. Asbestos yarns covered here are classified based on their structural component as follows: Class A, yarn consisting of asbestos fiber or asbestos and other fibers; Class B, yarn containing wire reinforcements; Class C, yarn containing organic reinforcing strands; Class D, yarn containing nonmetallic inorganic reinforcing strands; and Class E, yarn containing a combination of the reinforcing strands used in Classes B through D. On the other hand, the grades (Commercial, Underwriters', A, AA, AAA, and AAAA) of asbestos yarn are based on the percentage of asbestos content by mass. Yarns shall be sampled, prepared, tested and conform accordingly to physical (asbestos and reinforcement type and content), electromagnetic (magnetic rating and electrical insulation), mechanical (tensile or breaking strength), and dimensional (yarn number, twist direction, and number of turns per unit length) property requirements.

1.1 This specification covers asbestos yarns having a minimum of 75 % asbestos fiber by mass, excluding the mass of other inorganic reinforcing strands which may be present.

1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.3 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 chrysoltile asbestos, refer to "Safe Use of Chrysotile Asbestos: A Manual on Preventive and Control Measures."

1.4 The following safety hazards caveat pertains only to the test methods, Section , described in this specification: 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 and health practices and determine the applicability of regulatory limitations prior to use. See 1.3 for a specific safety hazard statement.