The influence of longitudinal ventilation systems on fires in tunnels

Many tunnels are equipped with longitudinal ventilation systems to control smoke in the event of a fire. However, the influence of such ventilation on fire development and fire spread has rarely been considered. This paper pr esents the results of a study investigating the influence of forced longitu dinal ventilation on car fires, pool fires and heavy goods vehicle fires in tunnels. A Bayesian probabilistic approach is used to refine estimates, ma de by a panel of experts, with data from experimental fire tests in tunnels . Results are presented and the implications are discussed. The influence o f longitudinal ventilation on heavy goods vehicle fires is predicted to be much larger than the experts' estimates, causing a fire to grow ten times l arger than if natural ventilation was used. The effect of ventilation on a pool fire in a tunnel depends on the size of the pool; the heat release rat e of small pool fires mag. be reduced by forced ventilation, whereas it may be enlarged for large pool fires. The size of a car fire is not expected t o be greatly affected by forced ventilation at low ventilation velocities. (C) 2001 Elsevier Science Ltd. All rights reserved.