Fire Testing of Electrical Materials

In recent years electrical wire or cable insulation has been, once more, identified by NFPA statistics as a major material first ignited in residential fires (representing 7.6% of fires and 3.9% of fire fatalities in 1991–95) and the cause of 13% of catastrophic fires (1993–96). This highlights the need for renewed emphasis on fire testing of wires, cables and electrical materials. Cable fire tests can be subdivided into 5 categories: (a) Old fashioned small scale tests, which generally address only ignitability or flame spread, but the results of which are rarely meaningful in terms of real fire performance; (b) Vertical cable tray tests, of which there are a large variety, ranging in heat input from 20 kW up to 154 kW (in the case of riser cables), which address flame spread, and sometimes also smoke and heat release; (c) The Steiner tunnel NFPA 262 (UL 910) test, which determines wind aided horizontal flame spread, and smoke release, under a very high heat input (ca. 90 kW), with a relatively small mass load of cables; and (d) Small scale cable tests, often originally designed for materials, directed at measuring fundamental fire properties, such as heat release or critical fluxes for ignition or flame spread and thermal heating properties. (e) Tests for other cable fire properties, mainly smoke (obscuration, toxicity, corrosivity) and circuit integrity.