HRR fire, which is the order of magnitude for a car fire, the required ventilation velocity to limit smoke back-layering in a flat ceiling car park is around 1.1 m/s. When beams are present, the average velocity must be higher, particularly for longitudinal beams. If smoke is trapped inside a recirculation region, increasing the smoke extraction rate does not help to remove the smoke.

Temperature measurements are presented as obtained in a full-scale experimental campaign on large closed car park fires. Since the main objective of the study is the investigation of the impact of a smoke and heat control (SHC) system with forced mechanical horizontal ventilation on the smoke pattern in case of a car park fire, the desired fire heat release rate (HRR) is imposed by means of well-controlled liquid pool fires. Different parameters are varied: the fire HRR; the smoke extraction flow rate; the flow patterns (through modification of inlet air opening); and the presence (or not) of a transversal beam. Not surprisingly, less smoke back-layering is observed for lower fire HRR and higher smoke extraction rate, the effect of the latter being more important. The exact position of the extraction fans is not essential, when they are not close to the fire source. The impact of the flow pattern is substantial: when smoke is trapped inside a recirculation region, the smoke and heat are not removed effectively. A transversal beam can block the smoke, even for high HRR. The primary effect of jet fans (induction type, 50N) in the study at hand is a local cooling effect, not a significant impact on the global flow pattern. For the cooling effect to be observed, the jet fans must not be in a smoke filled region.