An experiment to test the potential for glass fragments to ignite wildland fuels
Klaus-Peter Wittich A C and Tanja Müller BA Agrarmeteorologische Forschung, Deutscher Wetterdienst, D-38116 Braunschweig, Germany.
B Institut für Geoökologie, Technische Universität Braunschweig, D-38106 Braunschweig, Germany.
C Corresponding author. Email: klaus-peter.wittich@dwd.de
International Journal of Wildland Fire 18(7) 885-891 https://doi.org/10.1071/WF08069
Submitted: 6 May 2008 Accepted: 15 October 2008 Published: 27 October 2009
Abstract
It is current opinion that glass fragments can serve as an ignition source for grassland, bush and forest fires by focussing sunlight. In order to check the validity of this assumption, ignition experiments were conducted in the open over six litter samples taken from forests in northern Germany. Of several glass fragments, the five bottle bottoms best focussing sunlight were installed 15–50 cm above the litter materials. We found that one bottle bottom was able to slightly char spruce needles, beech leaves and blades of grass. Although this particular bottle bottom let the temperature increase up to 327°C, flame formation did not occur. A secondary (but more realistic) experiment with a glass-bottle bottom lying on the litter led to a maximum temperature of 82°C in the space between the litter and the glass fragment.
Additional keywords: burning-glass effect, ignition experiments, light focussing.
Acknowledgements
The authors thank Dr Barbara Ubysz (Fire Protection Laboratory, Raszyn, Poland) for providing the report on the burning-glass experiments in Poland, Peter Lex and Professor Wolfgang Durner for helpful discussions, and Professor Johann Goldammer (Global Fire Monitoring Centre, University of Freiburg, Germany) for initiating a survey in the Fire Paradox Network with respect to the burning-glass effect. A single positive reply came from Spain from Domingo Molina: in summer 2003, a glass-induced fire occurred on an open southern slope.
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