Impact of cables on the fire safety of buildings. Part 2 - Cable fire properties

摘要

There is much uncertainty as to the contribution of cables to overall building fire hazard. In many cases the cable contribution to fire loading is small with minimal potential heat release and relatively low effluent toxicity. Recognised exceptions are computer server rooms, building service entrances and underground cable tunnels where the cable polymeric content may be significant and even the sole source of combustible fuel. A further problem is that the established fire cable tests are largely prescriptive. Cables are classified according to agreed generic pass/fail levels as opposed to a real cable installation related performance based criteria. The resulting cable classifications give little help in the prediction of the actual fire hazard. The fire properties of cables installed in buildings within the European Union will be determined using the procedure EN50399. In July 2013 the construction product directive will become a regulation and all CE labelled cables must be marked with a Euroclass defining their reaction to fire performance level as determined using the EN 50399 test method. The purpose of our paper is to demonstrate how by means of relatively simple modification the prescriptive EN50399 cable fire test can be used to generate fire safety engineering data to permit a realistic assessment of fire hazard. The procedure will be outlined using real fire test data obtained from both energy and communication building wire. The communication cable installations will include examples of both fibre optical cable and fibre unit duct installations currently being used to bring fibre into multi dwelling units.