Smouldering is a flameless form of combustion, deriving its heat from heterogeneous reactions occurring on the surface of the fuel when heated in an oxidizer environment. Smouldering is of interest both as a fundamental combustion problem and as a practical fire hazard, for instance in industrial storage units [1]. Many materials can sustain a smouldering reaction, among them wood pellets, which are becoming more widely used as an alternative to oil -fired central heating in residential and industrial buildings. Smouldering fires are difficult to detect, becoming a hazard that must not be underestimated [2]. The influence of varying the airflow, using two different configurations of smouldering combustion was studied: reverse and forward propagation. These are defined according to the direction in which the smouldering reaction front propagates relative to the oxidizer flow. In reverse smouldering, the reaction front propagates in the opposite direction to the oxidizer flow. In forward smouldering the front propagates in the same direction as the oxidizer flow: convective transport is in the direction of the original fuel ahead, preheating it before the smoulder zone is reached.