Toward safer firefighting strategies and tactics

Abstract

Adverse weather conditions and fuel accumulation may induce destructive fires. Therefore firefighters are highly exposed to fire entrapments, i.e. to be caught by the fire heat or smoke. As there are several types of fires, firefighters face different types of mitigation difficulties. They also face different situations potentially leading to entrapment. We suggest here ways to implement safer mitigation practises at both strategical and tactical levels. We analysed 103 firefighters’ entrapments described in both publications and internal reports from fire agencies across Europe, Australasia and North-America. We distinguished three types of fire (i.e. topography-influenced, wind-driven and convective-dominated fires) and we assessed the potential contributions of dynamic fire behaviours in entrapments for each fire type. The dynamic fire behaviours investigated are changes in wind direction, steep slopes prone to flame attachment and leeward slopes prone to vorticity-driven lateral fire spread. Our results show that 94% of the entrapments in topography-influenced fires have happened on steep slopes prone to flame attachment. We also point out that slopes prone to vorticity-driven lateral fire spread have been the most prominent factor associated with entrapments during wind-driven fires. Finally, in convective-dominated fires, many configurations can lead to entrapments, including those without any obvious dangerous fire behaviour characteristics. Whereas our study took months to identify risks associated to each fire type, firefighter commanders have to take mitigation strategic decisions within few minutes. On the field, crews have an even shorter decision time to choose safe and efficient tactical options. This is why dissemination of the fire type concept and consequent safety issues should be declined in several levels and time lags within fire agencies. At the top level of scientific understanding, fire behaviour analysts should be able to forecast the expected fire type in relation to weather, fuel and topographic inputs. They should both produce maps of dangerous areas, trigger points, key points, and assess the expected efficiency and danger from different strategic options. Incident commanders, division commanders and other command staff should be aware of the general behaviour of a fire regarding its type. They should also be informed of the associated areas at risk and the most efficient strategies to fight the fire regarding its type. Finally, crews should be trained to recognise risky zones on the ground and to egress rapidly such zones before dangerous conditions get aligned.