A repulsor vent was a device that blocked off the toxic lava fumes of Mustafar. The foundry of the Klegger Corp Mining Facility was installed with a repulsor vent system to prevent the potent fumes from being inhaled by organic lifeform. When the newly-built Fortress Vader came under an outbreak of lava fume that drove its Imperial lava troopers insane, the Imperial officer sent to handle the matter suggested to Darth Vader that the Empire evacuate his fortress until environmental filters were installed. Eventually, the lava fumes were blocked off from Darth Vader's castle, although traces of it continued to seep through its dungeons.