Simulation of flames and smoke spreading in an underground garage under different ventilation conditions

Abstract

Garages are significantly endangered by the formation and spread of fire. Additionally, some building equipment or installations located in a garage such as air outlets from ventilation installation could significantly deteriorate the fire situation. To determine the influence of the AHU (Air Handling Unit) outlet inside the garage on fire spreading, a simulation was carried out using the FDS (Fire Dynamic Simulator) in the PyroSim computer software. The investigated underground garage consists of 11 separated parking bays. The following conditions of a fire source were assumed: a car with a petrol engine, a fire area - 10 m2, a range of fire - 12 m, and a total power of fire - 4 kW. The simulations were carried out for two fire scenarios: 1) normal condition (AHU is disabled), and 2) airflow from an AHU outlet (5,200 m3/h). The results show a negative effect of an AHU on fire spreading. The temperature and the concentration of smoke during fire are 2-3 times higher than if an AHU operates. In both fire scenarios, the safe temperature for humans, i.e. 60°C at a height of 2 m above the floor level has been exceeded in less than 4 minutes.