Damper

Valve in a flue or chimney, by which the flow of hot gases may be checked and combustion retarded in the fire. Two types are used: 1st, the swinging or butterfly, mounted on a horizontal axis, about which it swings; 2d; the sliding or guillotine, or gate in which a flat plate slides in a frame to close the pa age. The first kind is self-balanced. Automatic regulation is often attained by connecting a weighted lever to the damper, the weight being raised to close the damper by pre ure of steam under a flexible diaphraghm, when the pre ure exceeds a certain amount.