| CPC F04D 29/422 (2013.01) [F04D 29/4226 (2013.01); F04D 29/4246 (2013.01)] | 18 Claims |

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1. A housing for a centrifugal blower, the housing comprising:
a first wall and a second wall forming a primary exit;
a third wall and a fourth wall forming a secondary exit;
a volute tongue between the second wall and the fourth wall; and
a moveable flap pivotally coupled at the volute tongue and extending toward the primary exit, wherein the moveable flap is configured to pivot between a closed position in which the moveable flap is flat against an interior surface of the second wall and an open position that defines an open angle between the moveable flap and the second wall.
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