| 摘要 |
An air flow reversal prevention door is mounted to a discharge opening of a ventilation fan. The door includes a frame member with a void in it to permit air flow to pass through the frame and is attached fixedly to a shaft which supports the door and is located between the door and a discharge opening of the ventilation fan. While the door is held open by air from the ventilation fan, the frame member is moved from the edge of the discharge opening toward the door and back and this enables the shaft to rotate because it is fixedly attached to the frame member and it causes the shaft to rotate with movement of the frame member. This causes the shaft to rotate through the entire range of motion of the door between its open position and its collapsed position. This tests the operation of the door without turning off the fan. Whenever the fan fails or is turned off the air flow ceases and the door collapses by gravity toward the discharge opening to prevent air reversal flow.
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