(under subclass 196) Subject matter comprising a means which senses pressure or direction of air flow to or from a ventilated space and which acts to allow airflow under certain sensed conditions and to obstruct airflow under other sensed conditions.
(1) Note. The means usually permits flow in one direction along a conduit while blocking flow in an opposite direction.
SEE OR SEARCH THIS CLASS, SUBCLASS:
3+, for a backdraft preventer incorporated in chimneytop or stacktop structure, particularly subclass 26.
70+, for condition responsive pressure maintenance inside a vehicle which may include a valve.
194, for a blast or shock wave type of backdraft preventer.
238, for pressure regulation of a ventilation system which includes both inlet and outlet airways.
255, for pressure regulation of a ventilation system which includes an inlet airway. 259, for a backdraft preventer and an inlet airway.
340, for pressure regulation of a ventilation system which includes an outlet airway.
353, for a backdraft preventer and fan for an outlet airway.
359+, for a backdraft preventer for an outlet airway.
