The regulation for places of public assembly demands fire protection measures between stage and auditorium, which is supposed to be normally closed and should only be opened for rehearsals and performances. This protection is realized by iron curtains – a fire and pressure resistant steel construction which closes the proscenium opening. Iron curtains are lifted by electronic or hydraulic drives and they close in case of fire by their own weight without any external energy. A falling brake smoothes the setting of the iron wall on the stage.
In order to desmoke the stage area in case of a fire, openings on the roof or in the side of the walls of the stage tower, which open automatically, can be installed additionally to the ventilation systems. In the roof area, usualy systems are slidable openings in the roof or flaps or hoods with hinges on one side, which lift up parts of the roof or the whole roof.
In order to guarantee an opening of the outlets without any energy, either they are opened by their own weight as used at the construction of the slideable systems, or by use of counterweights. In the case of hydraulic systems special preassure accumulators are installed.