Fire Safety Science Digital Archive

Results are presented for the vertical fire propagation for 0.508 and 1.29 m long electrical cables i n oxygen concentrations of 40 and 30%, respectively. The bottom 40% of the 0.508 m long cable and 16% of the 1.29 m long cable are exposed to external heat flux with a peak value of 50 kW/m. In the experiments, measurements are made for heat release rates, generation rates of chemical compounds and optical density of smoke The vertical fire propagation rate for cables is found to be proportional to the ratio of the chemical heat release rate to thermal response, a relationship suggested by various fire propagation theories. Conditions where self-sustained fire propagation is not expected to occur have been identified: 1) critical or minimum heat flux for ignition > 20 kw/m²; 2) vertical fire propagation rate V < 1.0 x lom3, Hs; and 3) chemical heat release rate/thermal response-< 0.55 see'. These conditions are satisfied in larger-scale fire propagation experiments for cables. The analysis suggests that it is possible to design a small-scale standard fire test for cables based on ignition, fire propagation and heat release rate