| 摘要 |
A ventilator device comprises a casing having one or more openings for passage of ventilation air therethrough, a shutter within the casing and normally held retracted from said one or more openings, first means for urging the shutter to a position to close the one or more openings, and second means actuation of which releases the shutter to cause it to be moved by said first means to close said one or more openings. |
