Bench-scale flammability testing to optimize the effectiveness of fire retardant treatment of wildland fuels

This work focuses on evaluating the effectiveness of fire retardants, using bench-scale flammability apparatuses to test Pinus radiata D. Don needles. Two devices entirely developed in Chile, representative of continuous and discontinuous ignition modes, were used. The product tested was Phos-Chek LC65A-Fx, commonly used in wildfire fighting operations in Chile. The retardant was applied on the pine needles at different concentrations in order to study the effect of retardant concentration (${\sigma }_{ret}$) on different flammability parameters. Notable findings include a modification in flame behaviour in treated samples, with reduced smouldering and prolonged flame duration. As expected, the ignition delay times increase with the amount of retardant, showing a similar behaviour as the heat release rates (HRR). Interestingly, the critical heat flux (${\dot{q}}_{cri}^{\prime \prime }$) corresponding to spotting ignition was not affected by the addition of retardants, although an increase in ignition times ($t_{ig}$) was noticeable. Experimental observations underscore distinct flame dynamics, highlighting the potential of retardants to impede fire propagation. This study highlights the crucial role of retardants in fire management strategies and emphasizes the need for optimal application, especially in urban areas adjacent to forests.