Abstract: A natural green phosphate salt additive sodium phytate is selected as a fine water mist additive and compared with the commonly used phosphate salt additive ammonium hypophosphite. Two inert gases （N2, CO2） are selected, and the additive fine water mist and additive fine water mist-inert gas composite extinguishing agent were used to extinguish ethanol and n-heptane fires by independent design and construction of a cup burner experimental device for studying gas-liquid fire extinguishing media. The experiments were carried out on ethanol fire and n-heptane fire, and the mechanism of fire extinguishing effect was evaluated by establishing a quantitative model of physicochemical inhibition of fire extinguishing agents. The results show that the addition of two phosphorus salt additives can improve the fire extinguishing effect of fine water mist, 1% and 3% mass fraction of sodium phytate improve the effect more obvious than ammonium hypophosphate, and sodium phytate fine water mist is the best fire extinguishing concentration. Sodium phytate fine water mist at 3% mass fraction has the best fire extinguishing efficiency, 5% mass fraction of that is not as good as pure water fine water mist. The minimum fire extinguishing fraction continues to decrease with the increase in mass fraction of ammonium hypophosphate fine water mist. For the gas-liquid composite extinguishing agent, inert gas on the fine water mist extinguishing efficiency has different degrees of improvement, and CO2 is more effective compared to N2. Meanwhile, for the same type of extinguishing agent, evaluated by quantitative model, the chemical coefficient of the extinguishing agent and the extinguishing efficiency are with good correspondence.

Key words: cup-burner, fine water mist, inert gas, quantitative models, potassium salt additive