Fire Safety Science Digital Archive

Car parking has developed differing technologies. Fire protection techniques have to develop accordingly to ensure the optimum levels of protection. In the present case the parking technology allowed the design of a 10 storey high, enclosed car park with fire-resisting outer walls. Cars are parked in open-fronted (fire-resisting) concrete cells by automatic machinery which operates through an atrium-like space through the entire height of the building. Maintenance and fire service access is via routes outside this large, single fire compartment; opening via fire-resisting doors into the rear of each cell. During normal operation, the entire multi-storey fire compartment is unoccupied. This means in turn that there is little difficulty in meeting the requirements under the Building Regulations. Zone model methods are used to assess whether the initial fire cell is likely to flash over, increasing the size of the fire and developing a threat of fire spread to the cell immediately above. It is suggested that for cells larger than 3-car, there is a likelihood of “runaway ignition” leading to loss of the building. For unsprinklered cells of 3 or fewer cars a smoke and heat exhaust ventilation system protecting fire-fighter access and/or minimising damage to cars on higher storeys, needs to be of an impractically large fan capacity of about 110 m³/s to 150 m³/s. The same methods show that, with sprinklers to prevent flashover in a cell, the fan capacity needed to allow fire-fighter access with good visibility reduces to around 30 m³/s or to about 38 m³/s to prevent damage to cars on higher storeys. Design fires, both sprinklered and unsprinklered, are based on the recently published BS 7346-7: 2006 which assumes sprinklers will allow the original vehicle to continue burning while preventing spread to adjacent vehicles.