Research Letter 24

BUTT OUT?

It is December and in the Southern Tablelands of NSW and the ACT fire outbreaks will take on a new significance as pastures cure and forests dry out after a particularly wet spring. The early spring pulse of serious fire starts that spread south along the coast of NSW from southeast Queensland is over and the summer pulse of fire outbreaks on the southern Tablelands will soon be under way. In western NSW there are vast areas of ephemeral grasses, more than at anytime since the ‘big fire year’ of 1984 according to some observers.

For those interested in the seasonal changes in fire weather (Forest Fire Danger Index) from the coast of southern NSW to the inland and thence to Adelaide, see Gill and Moore (1990). For more detail, the changes in fire weather from the coast at Wollongong, thence to Sydney and Katoomba in the Blue Mts, may be seen in Gill and Moore (1994).

As the summer fire season progresses we will hear more and more that: “the fire was believed to be caused by a discarded cigarette butt”. However, there is considerable doubt about the significance of the smouldering cigarette in setting fires (Weber 2000). Has the blame put on smokers for bushfires been unjustified? Just knowing the cause of a fire is difficult enough (see Crowe 2000 in relation to arson fires), so how can we know that a cigarette was the cause? If a butt was found in a likely spot, how do we know that this was the cause or just a ‘dead’ butt in the right place?

Can cigarette butts, discarded alight, cause bushfires? Possibly, even probably, but .... The work of Markalas (1985) is the only experimental study of the subject that I could locate. We might quibble with the results because the work was done in a European context and in a laboratory but the same principles probably apply here. Markalas found that:

In the field at ground level the wind speed is likely to be slight and fuel moisture greater than oven dry. Conditions in the field are never likely to be as favourable for ignition as those in Markalas’ laboratory experiments. However, a lighted cigarette flicked from a car travelling at 80km per hour or more may have a temporarily increased burning rate thereby making it a more significant source of ignition than it otherwise would have been (P.H.R. Moore, personal communication). On present evidence, cigarette butts are likely to be a poor ignition source but a possible ignition source none-the-less; the verdict is unclear.

Butting out before disposal of cigarette ends is wise; casual disposal of butts – lighted or not - may be illegal!

References:

Crowe, F. (2000). The arsonist’s mind. In: National Academies Forum. Fire! The Australian Experience, Proceedings from the National Academies Forum seminar held at the University of Adelaide, SA, 30 September – 1 October 1999. Pp. 45- 50. Australian Academy of Technological Sciences and Engineering Ltd., Melbourne.

Gill, A.M. and Moore, P.H.R. (1990). Fire intensities in eucalypt forests of south-eastern Australia. Int.Conf. Forest Fire Research, Coimbra, Proc. B.24,1-12.

Gill, A.M. and Moore, P.H.R. (1994). Some ecological research perspectives on the disastrous Sydney fires of January 1994. Proc. 2nd International Forest Fire Research Conference, Coimbra, Portugal. Pp. 63-72.

Markalas, S. (1985). Laboratory experiments on the role of cigarette ends in lighting fires. Allgemeine Forstund Jagdzeitung 156, 193-197.

Weber, R.O. (2000). Bushfire causes. In: National Academies Forum. Fire! The Australian Experience, Proceedings from the National Academies Forum seminar held at the University of Adelaide, SA, 30 September – 1 October 1999. Pp. 39- 44. Australian Academy of Technological Sciences and Engineering Ltd., Melbourne.

A. Malcolm Gill

December, 2000


This is the last Research Letter of Series 1. I have enjoyed writing it. It is appropriate that I thank Peter Moore, my former (“former” because I have retired from CSIRO) Senior Technical Officer for vetting the Letters for me. The Letters were all the more readable because of his input.