On the ignition hazards of combustible liquid: the case of S-lactic acid water solution

The simultaneous exceedance of the flash point and the presence of an external source of ignition such as electrostatic sparks or hot spots lead to a flame-related scenario. Nevertheless, anomalous behaviour can be observed if the liquid is subject to thermal degradation, even below the flash point. This work is dedicated to the specific case of the hazard of combustible liquids due to the insurgence of secondary reactions activated by an ignition source and a constant heat flux to the sample within the range 7 kW/m2 and 50 kW/m2. To this aim, an aqueous solution having 90 %w lactic acid has been analysed experimentally by calorimetric analysis. The temperature of the liquid, the mass loss rate, and the heat release rate for the pool fire of lactic acid have been measured by a cone calorimeter. Results were compared with experimental data from the literature and theoretical data. The use of flash point temperature (regardless of the approach adopted for its evaluation) has been found to lead to non-conservative results on the safe side. Based on the collected data, the use of a cone calorimeter is recommended to evaluate the ignitability of liquid substances exposed to heating sources such as fires.