1.1 This specification covers the composition, dimensions, and physical properties of flexible unfaced foam sheet, used to insulate interior surfaces of HVAC ducts, plenums and equipment used for the distribution of conditioned air with a temperature of up to 250°F (121°C). 1.2 HVAC ducts, plenums and equipment systems typically operate between a temperature range of 50°F to 150°F (10°C to 65°C) and are designed to meet building code requirements of maximum temperatures of 250°F (121°C). 1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1.4 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 requirements prior to use.