Experimental study on fire safety of chimneys in real use and actual site conditions

In recent years, numerous building fires have occurred in Finland where the fire has started due to the ignition of flammable materials in the vicinity of metal chimney penetrations through floors, roofs and walls. Based on onsite observations and experimental studies, one possible reason for the ignition is that the actual flue gas temperatures in real use in buildings are higher than those assumed for chimney design. An experimental study has been conducted in the TUT Fire Laboratory at Tampere University of Technology to determine the actual site conditions, identify the difference between the actual site conditions and the EN standard test conditions and assess whether the differences affect the fire safety of chimney penetrations. This paper describes the results of five site tests conducted in four different residential buildings and a sauna. The results revealed that the actual use of fireplaces and site conditions may differ significantly from the test conditions of EN standards. The site tests demonstrated higher flue gas temperatures and stronger draughts than what specified for the EN standard tests. The flue gas temperatures measured onsite were 134° to 278 °C higher than the mean temperature indicated in the CE marking of the tested fireplaces. The results indicate that the flue gas temperatures given in the CE markings of fireplaces may be too low for the designing of chimneys. This may cause a fire hazard at chimney penetrations.