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[References: 42 tit.]

Specialists in forest fire extinguishing consider special fire retardants (solutions, suspensions, and emulsions), in addition to water, to be the promising. When discharged from aircrafts, these agents show greater efficiency in suppressing combustion and preventing ignition of forest materials compared to water. However, such agents have been developed through trial and error so far, because no general theory of the effect of aqueous suspensions, solutions, and emulsions on combustion has been developed yet. In addition, there have not been any experimental data to develop physical and mathematical models of processes when a combustion front acts on forest materials after their wetting by special aqueous compositions. In this paper, we studied the wetting behavior of water and four special fire retardants (bentonite suspension, bischofite solution, fire-extinguishing solution FES-5, and foam agent emulsion) on surfaces of leaves, branches, and needles. The lifetimes and evaporation rates of droplets of fire retardants from the leaf surface were determined at 50–110°С. The differences were established in the evaporation rate of droplets of typical fire retardants and water without additives. With identical initial droplet sizes of fire-extinguishing suspension, emulsion and solutions, their evaporation times differed significantly.