片语
south ventilation shaft南风井
ventilation of mine shaft矿井通风
ventilation shaft reconstructing风井改造
a ventilation shaft排气孔
surface mine ventilation shaft地面风井
emergency ventilation shaft事故通风井
tunnel l ventilation shaft隧道通风井
uranium mine ventilation shaft铀矿井通风
piston ventilation shaft layout活塞风井设置