Cases where smoking/accidental discard has been raised as a defence are sometimes dismissed on the basis that the timeframe was too long or too short for a fire to occur. In a recent Crown Court trial, a forensic scientist specialising in fire cases told a jury that it takes more than 30 minutes for a lit cigarette (placed in suitable fuels) to turn into flames, and with a hand-rolled cigarette suggested that it was not possible. This opinion is not uncommon, but not necessarily correct.
In recent tests conducted by KBC, a commercial cigarette was positioned within shredded paper and tissue in a waste paper bin and placed outside where a light breeze was blowing. Flames were seen in just over 5 minutes.
We found hand-rolled cigarettes tended to go out within a few minutes without causing a fire, however a fire investigator in the US has reported that, during tests done on a very windy day, even a hand-rolled cigarette could lead to flames in the same timeframe.
The amount of ventilation can radically change the propensity and time it takes for a cigarette to set fire to things like paper, cotton, cardboard or sawdust; consequently this must be a factor taken into consideration when ruling in or out possible causes.
Dr David Schudel BSc, PhD, D-ABC, CChem, MRSC, CFI