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

In recent years, there have been numerous building fires 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 on-site 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 assumed for chimney design. An experimental study has been carried out in the TUT Fire Laboratory at Tampere University of Technology to determine the actual site conditions, to identify the difference between the actual site conditions and the EN standard test conditions and to assess whether the differences affect the fire safety of chimney penetrations. This paper describes the results of five site tests which were conducted in four different residential buildings and in a sauna. The results revealed that the actual use of fireplaces and the site conditions may differ significantly from the test conditions
of EN standards. The site tests demonstrated higher flue gas temperatures and stronger draughts than specified for the EN standard tests. The flue gas temperatures measured on site 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 dimensioning of chimneys. This may cause a fire hazard at chimney penetrations.