Patent ID: 8910516

Claim:
A device for detecting directional differential pressure between two spaces, comprising: an elongated conduit arranged to be coupled with a wall separating a first space from a second space, the conduit having openings at opposite ends that permit fluid flow through the conduit from the first space toward the second space, the conduit arranged to be inclined with respect to a horizontal reference plane such that a first region of the conduit associated with the first space is vertically lower than a second, vertically higher region of the conduit that is associated with the second space; at least one movable element disposed within the conduit adapted to be moved from the first, vertically lower region of the conduit to the second, higher region or from the second higher region to the first vertically lower region, in response to a differential pressure between the first and second spaces; and a differential pressure set point indicator configured to correlate each of a plurality of angles of inclination of the conduit with respect to the horizontal reference plane to a respective threshold differential pressure between the first and second spaces that is sufficient to cause the at least one movable element to move from the first, lower region of the conduit to the second, higher region.