Cigarette Induced Smouldering Fires and Time to Transition ...

1 Fire&Arson Investigator July2014 25 Cigarette Induced Smouldering Fires and Time to Transition to FlameCigarette Induced Smouldering Fires and Time to Transition to FlameDavid Schudel, Keith Borer Consultants, Locard House, Belmont Business Park, Durham DH1 1TW. United KingdomEmily Hazell, c/o Keith Borer ConsultantsThe time it takes for a Cigarette to Transition to a fl ame can impact the consideration of potential fi re causes and may be a critical component in your fi nal hypothesis. Babrauskas1 discusses such an example whereby the timeframe to a fl aming fi re was considered too short to be the result of a Cigarette and the defendant found guilty of arson as a result.

2 This was reversed on appeal when data was available that showed the shorter Transition times to fl ames. The ability of a Cigarette to ignite cellulosic materials (materials made from plant fi bre, such a cotton or paper) has been well studied over the years. Early work was done on furniture items by Braun et al at the National Bureau of Standards2 which was followed by a literature review by Krasny in 19873. Braun s tests found ignition of cotton upholstery in as little as 22 minutes. DeHaan4 reported the same result with older, cellulosic-fi lled upholstered furniture and bedding, and adds that this could be as little as 18 minutes if the fabric cover was torn and the Cigarette placed in the stuffi ng.

3 Fire Findings5 conducted tests on waste paper bins using a large selection of fuels. They found that in 5 occasions out of 300 tests a discarded Cigarette led to fl ames being produced. In one test, the result was attributed to the presence of oil from a popcorn bag along with other fuels; the other 4 are not described. Hollyhead6 wrote a fairly comprehensive review published in 1999 that reported a test where tissue and paper were crumpled up and placed in a draught free basement. Flames were found after only 12 minutes after the introduction of a Cigarette .

4 He recommended that a minimum time of 10 minutes be considered for a Transition to fl ame for a Cigarette ignited fi re. Although useful, this recommendation is at odds with that discussed by Cooke and Ide some 14 years earlier7. Further tests by Fire Findings8 found that in 500 tests of cigarettes on fabric, not one created any fl ames up until the point that a draught was introduced. This is one of the few real-world tests where conditions were not tightly controlled. They found that a gentle breeze was enough to allow cotton to be ignited and Transition to fl ames on a consistent basis, although they did not provide any timing information.

5 As mentioned above, Cooke and Ide7 commented on the presence of draughts in the Smouldering process and how it can dramatically In a recent case in the UK, a forensic fi re expert told the jury that it took at least 30 minutes for a lit, discarded Cigarette to produce fl ames in cellulosic materials. This is not the fi rst time we have come across this common misconception in fi re investigation reports in the United Kingdom. Continued on pg. 2626 Fire&Arson Investigator July2014accelerate the process of Transition to flame. They reported a draught of around 1m/s (about 2 mph) could produce free flaming in corrugated-cardboard cartons that were in contact with a Cigarette within 5 minutes.

6 Despite the effect of a draught on a Smouldering fire, many tests were done in non-draught or low airflow conditions. In recent years, the introduction of Reduced Ignition Propensity cigarettes (with its tongue-in-cheek acronym RIP cigarettes; also called Fire Safe Cigarettes or FSC) might be expected to affect the potential for Smouldering ignition leading to flaming. These cigarettes contain bands in the paper wrapper that are designed to halt Smouldering at the band point if air is not actively drawn through the Cigarette . Tests undertaken by one of the authors of ten RIP cigarettes found five of them stopped at a designated band, whereas five burned to completion.

7 This short test reflects other tests such as those published by Fire Findings9 who tested a large number of cigarettes and found that the ability of the banding to halt Smouldering was highly variable especially from brand to brand. Additionally they placed 150 of these types of cigarettes into paper trash and found flaming combustion in two cases, reflecting their earlier published work on this5. In the UK, hand-rolled cigarettes are commonplace and there is a generally held belief that they have far less propensity to start a fire simply because they tend to self-extinguish when not actively smoked ( have air being drawn through them).

8 A similar argument applies to cannabis cigarettes (which can be made using tobacco mixed with cannabis or cannabis on its own). The action of hand-rolling in itself will produce cigarettes with varying combustion properties and so testing such cigarettes does include a certain amount of subjectivity when making a Cigarette . Notwithstanding, Andrew Justice10 studied hand-rolled and cannabis cigarettes his Masters thesis. He found neither type caused flaming ignition of cellulosic materials in his test conditions, which were based in a fume hood. However as an ad-hoc test he placed a hand-rolled Cigarette in a bin with some of the test material on a very windy day after which copious amounts of smoke were produced and, on placing the bin outside, flames quickly resulted within 5 minutes.

9 Justice repeated the test twice, the first with five hand-rolled cigarettes and the second three hand-rolled cigarettes. These were placed carefully in the bin so there were not touching or within close proximity to each other. He found the five hand-rolled cigarettes did not produce flames whereas the test with three produced flames within 4 minutes. As noted above, this was done in very windy conditions. Although he did not create flaming combustion in his fume hood test environment, Justice did find that of the 180 hand-rolled cigarettes he tested, 65 underwent full consumption leaving on ash behind.

10 Three of these were cannabis/tobacco mixes. Justice considers that the extent of insulation caused by the substrate the Cigarette was placed on or in was critical in ensuring the Cigarette continued to smoulder. He found Smouldering combustion in 32 of 72 tests where hand-rolled cigarettes were firmly insulated. For example, tightly wrapped Kleenex tissue smouldered on average for 23 minutes, compared to loosely wrapped Kleenex at minutes. The authors also conducted some empirical testing of their own. Metal, office-size (27 litre; 6 imperial gallon) trash cans were half-filled mostly with shredded paper and crumpled tissue although there was some cotton.