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.
