A fireproof cover, rolled out on a stainless steel ventilation duct, is directed by means of a servo mechanism. The whole unit is integrated in a galvanised steel casing with a thickness of 1.2 mm.
The screen starts to operate when it picks up a signal from the alarm installation.
Under normal conditions and when there is a current, the screen stays in position rolled inside the casing with the ballast bar at a predetermined level.
When the alarm sounds, the screen unfolds up to a predetermined height and at a controlled speed.