Abstract: A monitor for a gas appliance vent includes a conduit section that is mounted in line with a vent leading from a furnace or other gas appliance. The conduit section has an interior tubular plenum member which extends across the vent interior. The tubular plenum member has upstream facing openings therein. An outer end of the tubular member passes through an aperture in the conduit section. The outer end is open to allow flow therethrough from the upstream facing openings. A switch is mounted in proximity to the outer end. The switch is thermally responsive to respond to the heated flue gases that flow out the outer end. The switch is operably connectable to either an alarm or a fuel line shut off valve.

Abstract: A vent assembly adapted for venting into the atmosphere hot burner exhaust gases from the flue exhaust port of a heating appliance within an enclosure, such assembly including an exhaust duct and a relief duct. The exhaust duct is connected at one end to said flue exhaust port and is opened at its other end to the ambient atmosphere outside of the enclosure. A selectively responsive closure device, such as a thermally controlled damper, is disposed within the exhaust duct. The relief duct is connected to the exhaust duct at a point along the flow of exhaust gases upstream of the closure device and has a relief aperture disposed at a height between that of the exhaust port and that of the burner.