Fire Safety Science Digital Archive

The use of mechanical ventilation to protect high flats against explosions involving flammable gases or liquids is discussed in general terms. The relevant properties of the gases and vapours are considered, the extraction ventilation requirements are suggested, and application is made to a specific example (Flat 90, Ronan Point). The advantages of mechanical ventilation are that it would control the time for which a dangerous explosive volume of gas or vapour would be present, reduce the size of the volume, prevent an escape of gas from spreading to other rooms, and would prevent a slow leak from accumulating. The proposed mechanical ventilation should not cause discomfort to the occupants and should give good protection against explosions caused by leakage of town gas, likely leakage of L.P. gas, and moderate spillages (a few pints) of flammable liquids such as petrol. Some discussion is made of the problem of large spillages. The desirability of full scale tests on actual structures is stressed, particularly as regards the extent of mixing of flammable gas or vapour with air and the probability of forming a hazardous pocket in ventilated rooms. Also the extraction rates of unmixed layers and the mixing effect of heating systems should be investigated.