This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol6", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
Hitherto only the rapid exit of the people has been considered; but even the best arrangements in this respect may be insufficient if other principles are neglected. As before stated, nearly every fire originates upon the stage, and it is therefore essential that every effort should be taken to enable the stage to be immediately cut off from the auditorium in case of fire. The wall separating the two parts of the house should have no other opening in it than the proscenium opening, while communication between the two should be made through the external air. If, however, the latter cannot be effected, the necessary openings must be thoroughly protected with fire-resisting doors.
The proper protection of the proscenium opening is of the greatest difficulty, but may be effected when thoroughly considered with the questions of air currents. Rolling blinds of asbestos have shown themselves to be useless for the purpose. The construction of the screen, whether of asbestos or iron, must be thoroughly rigid and well stiffened, while, to make room for it when raised, the height of the roof above the proscenium opening must not be less than the height of the opening.