回风管道部分。可以指定单线管道或双线管道。
My vacation begins next week. I've got a return air ticket to my hometown.我下周休假,已经买好了回家乡的往返机票。
Tower 2 at core end needs a closed ceiling zone to hide the ducts of return air going into shafts.在芯筒尾部的2号楼需要有一段封闭的吊顶区域以隐藏回风管道进入斜井。