| CPC G01P 13/0066 (2013.01) [G01L 13/02 (2013.01); G01L 19/12 (2013.01)] | 25 Claims |

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1. A device comprising:
an inclined conduit to be in fluid communication with a first space and a second space when the device is installed on a barrier separating the first space and second space, the barrier having a first side facing the first space and a second side facing the second space, wherein an angle of inclination of the inclined conduit is adjustable with respect to a horizontal reference plane such that a first region of the inclined conduit is vertically lower than a second vertically higher region of the inclined conduit, wherein the inclined conduit adjustable along a plane transverse to the barrier such that the angle of inclination of the inclined conduit is adjustable relative to the horizontal reference plane, and wherein the angle of inclination of the inclined conduit is adjustable from only the second side of the barrier; and
at least one movable element movable within the inclined conduit from the first vertically lower region to the second vertically higher region in response to a differential pressure between the first space and the second space.
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