An experimental study on backdraught: The dependence on temperature

This paper presents the results of a series of reduced scale experiments to investigate the temperature conditions leading to backdraught in a fire compartment (0.8 m×0.4 m×0.4 m), using solid polypropylene pellets as the fuel. The factors of primary interest are the pre-burn time, before the fire becomes oxygen limited, the duration of door closure, and the temperature distribution in the compartment. It is shown that the temperature inside the compartment is crucial for the occurrence of backdraught. Above 350 °C, backdraught by auto-ignition is possible. If a pilot spark is present, backdraught may occur at temperatures down to 300 °C. It is shown that backdraught conditions can be achieved in the early stages of a fire as long as a suitable temperature is reached, at considerably lower temperatures than those generated during flashover. Further investigation on gas concentration is essential to understand the chemistry of backdraught combustion.