Abstract: A fire and smoke damper equipped with a thermal responsive electric switch for closing the damper responsive to the elevation of the ambient temperature above a first predetermined level. Control circuitry is provided for permitting selective override of the switch for opening the damper from a remote control panel so that toxic fumes and smoke may be vented through the damper. A second thermal responsive switch operable at a higher predetermined temperature is interposed in the control circuit to insure that the damper may not be opened by the override circuit in the event that such higher ambient temperature has been reached in the location of the damper.

Abstract: An improved actuator for the damper of a ridge vent. The actuator includes coil springs constructed from a shape-memory alloy. The springs are contracted below a selected temperature at which the damper is to open, and the contracted springs maintain the damper closed on its seat. Above the transformation temperature of the springs, they expand and raise the damper off of its seat to an open position for venting of air through the ridge vent.

Abstract: A fire damper operated by an air motor for incorporating into the pneumatic piping system of a building. The damper motor holds the damper open under the influence of pressurized air from the system. A valve actuator in the flow channel of the damper has a fusible link maintaining the actuator in a standby condition. Temperature sufficient to destroy the integrity of the link permits an abutment on the actuator to swing to a position allowing the valve member to shift to interrupt the air pressure applied to the motor. This closes the damper. The damper may also be closed independently of operation of the actuator by interrupting the flow of pressurized air to the motor.

Abstract: A hollow airfoil damper blade formed by sheet metal. The walls of the blade are formed by two sheets crimped together at the edges. The blade tapers from the center toward the edges and has two pairs of V-shaped stiffening ribs formed by corrugations in the sheets. The ribs project nearly one half the blade thickness to enhance the strength of the blade and its resistance to deflection. The ribs cooperate to form a channel which closely receives a stub axle in each of its ends to provide for pivotal mounting of the damper blade. The axles are contacted directly by and welded to each of the ribs.

Abstract: An access door which covers and seals an access opening in a ventilating duct. The edge of the access opening is strengthened by a dual density gasket having a U-shaped hard portion which is applied to the duct edge. A softer sealing element projects from the hard portion of the gasket and is sealed against from the inside by the door so that the duct pressure enhances the seal. The door is a sheet metal panel having a stepped configuration and a peripheral flange for contact with the seal elements. The door is held over the access opening by retainer straps having adjustment screws.

Abstract: A transversely circular fire damper having a butterfly type blade operated by a jack shaft spaced longitudinally of the housing from the blade axle. Linkage including an "over center" stop rotates the blade in one direction by operation of a motor coupled with the shaft. A clutch in the form of a pair of relatively telescoped members secured together with entectic solder is connected with the jack shaft and the motor so that the shaft is released from the motor when the ambient temperature reaches a point high enough to melt the solder. The jack shaft is spring biased in a direction to close the damper blade under such condition.