Experimental and theoretical investigation of an adjacent wall on the occurrence of flashover

In urban or informal settlement fires, the influence of an adjacent inert wall/dwelling on the fire development of the burning dwelling is still unknown. Therefore, 41 compartment fire experiments were conducted with a ¼ scale ISO 9705 room, with a calcium silicate board acting as the inert wall, was placed in front of the burning compartment's opening with distances between 50 and 1250 mm. Parameters such as the mass loss rate of fuel, temperatures of gas and walls, heat flux imposed on the floor, and time to flashover were analyzed. From the experiments, it was found that the flashover occurrence times differed significantly with or without the adjacent dwelling, and the time to flashover increased gradually with increasing distance from 50 to 300 mm between the burning compartment and adjacent wall, but decreased with distance from 300 to 600 mm. The heat flux to the floor was calculated and correlated well with measured values, confirming that the observed experimental phenomenon was primarily caused by the interaction between the combustion efficiency of fuel and the different heat losses from hot gas flowing out from the opening depending on the adjacent wall location. Moreover, a modified MQH method and a theoretical model were proposed to predict the gas temperature and time to flashover, respectively.