Tracking a Ceiling Jet Front for Hot Smoke Tests in Tunnels

There are difficulties in tracking the ceiling jet front while carrying out hot smoke tests in long tunnels with a small fire. In this study, an experimental method using infrared beams is suggested. The arrival time of the hot ceiling jet front to a designated position is measured by the abrupt attenuation of the infrared beam intensity. Field measurements are carried out in an underground tunnel of length 88 m. Diesel pool fires up to 1.5 MW are studied. The results on tracking the ceiling jet front are compared with the measurements by using the thermocouples, thermal resistors, and visual observations. This method is demonstrated to be useful for tracking the ceiling jet front at positions further away from the fire. Therefore, the method is suitable for studying the ceiling jet in hot smoke tests for evaluating smoke management systems in long tunnels.