| 摘要 |
A reduction motor 15 mounted on a trolley 16 sited in the basement unwinds the cable from the drum 4 which cable winds onto the drum 5 and allows the brush 3 fixed to a rigid structure 10, perforated to allow the passage of contaminated air towards the top ventilation 13, to be lowered. The axis 11 may be fitted with a heavy weight 12 at its bottom part. <IMAGE>
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