Fire Safety Experimental Investigations of Time to Flashover as a Function of Humidity in Wood

The fire in Laerdalsoyri, Norway, on 18–19 January 2014, developed faster than the fire fighters could handle, and strong winds quickly spread the fire to neighbor houses and 150 m downwind to distant houses. 36 modern buildings and 4 historic buildings of cultural heritage were lost. The cold low relative humidity air in the deep valley dried the structures and resulted in rapid growth of fire and fire spread. This has triggered studies to understand as to how early the flashover is reached when fuel moisture content (FMC) in wood goes to low levels especially in winter when heating inhabited structures is a necessity. A study of flashover as a function of the FMC in the wood has been carried out by conducting experiments on approximate equivalent of ¼ ISO rooms in the laboratory. The relative humidity and temperature in the ambient air are also noted. It is observed that low FMC is the main factor that leads to early flashover. The temperatures rise very rapidly once flashover is reached with higher heat release and increased radiated heat. Hence, it can be said that lower humidity levels that tend to be the fact in winter can lead to fast development of fire. This has to be borne in mind, and necessary precautions are to be taken to control the development and spread of fire and reduce the risk of major fire accidents.