| 摘要 |
An animal barn includes air inlets which are filtered to extract pathogens and a plurality of extraction fans for generating an air stream so as to draw replacement air into the containment area through the air inlets. Each fan has a housing mounted in a wall with an outlet duct extending through the wall to an outlet opening outside the wall. A damper flap is mounted on the fan suspended by a hinge at an upper edge so as to extend in a closed position across the opening in a mounting plate. The damper flap is movable to an open position under forward air flow from the fan and closes against a resilient deformable seal to seal the damper flap to prevent reverse flow of pathogen contaminated air through the fan housing when the fan is shut off. An adjustable abutment member can act to hold the flap partly open against opposing wind forces during low fan operation.
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