Shutter, Fire-Resisting : A shutter which, together with its frame, is capable of satisfying for a stated period of time the criteria of fire resistance with respect to collapse and flame penetration. (BS 4422(2))
H. J. Porter (Chairman - Technical Committee), Dictionary of Fire Technology, The Institution of Fire Engineers, The Victory Press (Leicester) Ltd. 1979 UK. (Fr Tech - Brit) {81}