... for ventilator. with good insulation, high pressure and large air volume character. Portable ventilator connect with flexible duct,with ... ship building or welding, laboratory ,warehouse to ventilate waste air,harmful gas,dust ect. features 1)saving energy 2)strong wind ... for underground cable maintaince,shipping making. 2)blowing bad gas when welding shipbuilding,canning,bridge. 3)exhaust for fire ...