Fire suppression efficiency of water mists containing organic solvents

Abstract

This paper investigates the fire-suppression ability of water mists containing various organic solvents—ethanol, 1-propanol, tetrahydrofuran, methyl acetate, and 1,2-dimethyoxyethane—which form minimum-boiling azeotropic mixtures with water. The key factors influencing the suppression efficiencies of the solvent-containing water mists were elucidated by measuring the evaporation rates, flash points, extinguishing times, and spray properties (droplet-size distribution, spray mass-flux density, and droplet velocity) of the mists. Suppression trials indicated that (i) heptane pool fires can be extinguished by aqueous solutions of ethanol and 1-propanol at solvent concentrations of 1.0–20.0 vol%, but are not consistently extinguished by the other three solvents, and (ii) the extinguishing times of aqueous ethanol and 1-propanol (despite their high flammability) are significantly shorter than those of a wet chemical (i.e., conventional fire-extinguishing agent). In a stepwise regression analysis, the fire-suppression abilities of water mists containing ethanol and 1-propanol were positively related to the spray flux density, spray velocity, and flash point, enabling an estimation of the extinguishing times. A correlation analysis demonstrated that a faster evaporation rate improves the fire-suppression ability. The results confirmed that ethanol and 1-propanol are effective additives to fire-extinguishing water mists. The study findings provide useful insights into the development of new water-mist fire suppressants, potentially making a large contribution to the reduction of fire-related fatalities and economic losses in industries.