Extinguishing efficiency of an ammonium carbonate-based water mist in an aqueous ammonia medium for class B fires

Abstract

This study investigates the fire suppression efficiency and multi-action mechanisms of a novel binary aqueous fire-extinguishing agent (AFEA) consisting of 50 wt% ammonium carbonate (NH4)2CO3 in an aqueous ammonia medium. Open-air fire tests were conducted using a specialized automated spray installation against standard Class 8B petrol and diesel fuel pool fires. The experimental results demonstrated that the (NH4)2CO3-based AFEA spray achieved a rapid knockdown of volatile A-92 petrol fires within 2.0 s, requiring a minimal consumed volume of 280 ± 6 mL and outperforming the reference 40 wt% K2CO3 solution four-fold. Furthermore, the proposed formulation was the only agent capable of successfully suppressing high-thermal-inertia Euro-5 diesel fuel fires within a mean time of 29.7 ± 0.6 s under open-space constraints, where conventional salt solutions and tap water failed. The performance is governed by a synergistic mechanism: the endothermic pyrolytic breakdown of (NH4)2CO3 inside the flame generates a complex mixture of gases, including carbon dioxide (CO2), water vapor (H2O) that dilute oxygen, while ammonia (NH3) undergoes oxidative reactions in the high-temperature zone, further depleting local oxygen. A preliminary engineering upscaling analysis for a full-scale RVS-400 vertical steel storage tank (57 m2 pool area) indicated that transitioning to this novel binary system could conceptually yield a 75.7% reduction in the required agent inventory (from 391.7 L to 95.4 L). These findings provide a useful technical foundation for the potential development of compact, rapid-response automated fire protection systems for industrial petroleum depots.