Assessing the mixed foam stability of different foam extinguishing agents under room temperature and thermal radiation: An experimental study

Foam extinguishing agents have suggested to be an important method for suppressing fires, where the foam stability is one of the key factors in determining the efficiency of fire-fighting. Thus, lots of studies related to foam stability have been carried out. However, the influence of mixed types and ratios of foam agents on foam stability is still unclear. This study focuses on the foam stability of mixed foam extinguishing agents, especially under the condition of the thermal environment. The effects of mixed type and ratio on foaming ability, drainage, coarsening and insulation characteristics are studied systematically. Results indicate that the stability of mixed foam with S addition would decrease when compared with pure AFFF and FP foam, as evidenced by the decrease in foaming height, drainage time, and foam lifetime. The addition of S to AFFF or FP would produce the wetter mixed foam. In addition, the stability of AFFF/FP mixed foam first increases and then decreases with the increase of FP addition, and reaches the peak value at the mixed ratio of 3:1. The variations of foam stability could be explained by the change of viscosity and structure of adsorption layer at gas–liquid interface. The results provide helpful guidance for achieving high effective utilization of different foam extinguishing agents.