Fire Growth and Acceleration

Abstract

The use of the terms "growth" and "acceleration" appears to be inconsistent in the literature and we believe this inconsistency has hindered our understanding of behaviour in the early stages of a fire. The development of a fire from a point ignition to some equilibrium state and the associated increase in fire size and intensity has been referred to variously as the fire growth (Pyne 1984); build-up (Luke and McArthur 1978); or acceleration (Chandler et al. 1983) phase of the fire. More specifically the "acceleration phase" has been used to describe the increase in rate of spread from ignition to a quasi-steady rate of spread (Luke and McArthur 1978, McAlpine and Wakimoto 1991). Characteristic curves showing the increase in rate of spread are illustrated for different fuel and weather conditions (Luke and McArthur 1978). Hypothetical models to describe these curves have been proposed by Cheney and Bary (1969), Van Wagner (unpublished) and McAlpine and Wakimoto (1991). They have been called acceleration curves and acceleration models. The terms growth and acceleration, however, represent different concepts that are not interchangeable. We would like to clarify these concepts and discuss the practical implications for fire managers.