Attempted ignition of petrol vapour by lit cigarettes and lit cannabis resin joints

A recent murder enquiry prompted experimentation to confirm and visually demonstrate that lit cigarettes are not a viable source of ignition of petrol vapour. In addition, tests comprising the attempted ignition of petrol vapour using hot and smouldering cannabis resin were also undertaken. A series of experiments was also designed to recreate circumstances specific to the crime under investigation by undertaking cigarette/joint ignition tests involving a mannequin clothed in a cotton garment onto which petrol was applied. The ultimate aim of the experiments was to produce a visual aid for use during court proceedings. Thirty nine (39) ignition attempts that involved exposing lit commercial cigarettes, hand-rolled cigarettes and cannabis resin joints to petrol vapour were undertaken; ignition was not achieved in any of the scenarios. In addition, a single attempt to ignite petrol vapour emanating from a pool of liquid fuel was effected with a smouldering piece of cannabis resin; no ignition occurred. In all cases the petrol was clearly present within the limits of flammability since ignition was subsequently effected using a naked flame.