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 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.

1.3 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 13, 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.