Fire safety of metal chimneys in real use in households

Numerous building fires have been reported, for example in Finland and Italy, where the fire has started due to the ignition of flammable materials in the vicinity of chimney penetrations through floors, roofs and walls. In 2012 metal chimneys caused over 70 % of all chimney-induced fires in residential buildings in Finland. However, the share of metal chimneys was only about 10 % of all the chimneys. Metal chimneys are relatively new in Finland and in order to better understand the reasons for these fires and to improve the fire safety of chimney penetration details, an extensive research program has been carried out in the TUT Fire Laboratory at Tampere University of Technology during 2010-2016. Several possible reasons for the fires have been identified. Laboratory and site tests demonstrate that there can be significant differences between the actual conditions on site and the conditions defined in European test standards. In the standard test for metal chimneys, the roof penetration detail is 200 mm of mineral wool. In Finland, the thicknesses of thermal insulation materials on the roof are typically 400 to 600 mm and the insulation can also be made of wood- or plastic-based materials. In these conditions flue gas temperatures much higher than given in the CE marking have been measured. In this paper the research program, experimental testing and the key findings are introduced.