The converse of combustible. (1) Not capable of undergoing combustion. (2) Capable of satisfying the performance requirements specified in BS 476 pt 4 for building materials. (BS 4422(1)) The term incombustible is deprecated
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}