UL 793

Description / Abstract: These requirements cover automatically operated roof vents for smoke and heat that fall into two general categories: mechanically-opened and gravity-opened. Mechanically-opened vents consist primarily of a body frame, one or more damper covers and hatches, and operating mechanisms which generally include a heat responsive device and spring(s). Gravity-opened vents consist primarily of a body frame and nonmetallic drop-out panel. The vents covered by these requirements are operated manually or automatically in the event of fire to remove smoke and heat from the building. Automatic operation does not depend on electrical power or other energy sources that may be interrupted during a fire, but rather depends upon operation of a heat responsive device or on the action of a plastic cover shrinking and falling from place due to fire exposure, or the like. These vents are not intended for use as general purpose building ventilation devices.