| 摘要 |
A pressure differential indicating apparatus having a wall duct with first and second ends, first and second flange like mounting plates respectively disposed around and attached to the first and second ends, and a low speed airflow indicator mounted at one of the ends on a side of the mounting plate opposite that to which the wall duct is mounted. The low speed airflow indicator is adapted to indicate a specified pressure differential or range of pressure differential across a wall. The wall duct is preferably an adjustable length wall duct having two sections, a first section attached to the first mounting plate and a second section attached to the second mounting plate, wherein one of the two sections is constructed so as to be slidingly disposed in and in sealing engagement with the other of the two sections. The airflow indicator may be mounted within an extension of a clear plastic form of the duct second section. The extension extending past the mounting plate on the side of the wall on which the indicator is disposed.
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