| 摘要 |
An arrangement of casings 1, for the removal by suction of contaminated air from an area under and near the casing, comprises a downward-opening casing, at least one suction opening 6 arranged within the casing, which opening is connected to a suction member for effecting an air flow from below, into the casing and out through the suction opening for removal of air from the arrangement, means 10-18, 28 for returning part of the air sucked out of the casing to the area around a lower edge of a side wall of the casing, and members 23, 32', 34 for directing this air in a stream from the said edge 22 towards the interior of the casing so that secondary flows of air into the casing are induced at its edge area. The said means comprises at least one other suction opening 10, separated from the first suction opening 6, for sucking up the air for the said stream, whereby all the air drawn through the first suction opening is removed from the arrangement. The second suction opening 10 is arranged nearer the casing side wall 4, which terminates at the said bottom edge, than the first suction opening 6. The second suction opening 10 is arranged essentially at the top within the casing, at least in the upper half of the casing. <IMAGE>
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