Keywords: gas explosion, residential buildings, NFPA 921, scientific method, forensic engineering, welding operations, modelling, vapour diffusion, natural ventilation, LPG permeation, liquefied petroleum gas, air–LPG mixture
Forensic engineering applied to the analysis of a gas explosion in a residential building
Present paper deals with the identification of the cause of an explosion in a hollow space positioned below a residential building as the result of welding operations. On field investigation clearly demonstrated that the explosion was due to the ignition of a flammable atmosphere in the basement of the building. Along the trial two hypotheses were brought to the judge: (a) explosion of an air–petrol mixture (b) explosion of an air–LPG mixture. Forensic engineering techniques have been applied in order to assess which hypothesis was the correct one, on the basis of the observed post–accident scene. Modelling of the vapour diffusion, the natural ventilation and the permeation of LPG through the soil showed that possibility (b) was by far the most likely.