Fire-suppression efficiency and extinguishing mechanisms of calcium acetate using heptane cup-burner flames

To address the global requirement for a phosphorus-free fire-extinguishing agent, this study elucidated the ability of calcium acetate to extinguish cup-burner flames. The inhibition efficiency of calcium acetate powder (<50 μm) was compared with that of silica-uncoated ammonium dihydrogen phosphate (<50 μm), a chemical contained in agents used in typical ABC fire extinguishers. Calcium oxide and calcium carbonate powders were also used to investigate the suppression mechanisms of calcium acetate. The cup-burner experiments demonstrated that (i) calcium acetate, calcium hydroxide, and ammonium dihydrogen phosphate could extinguish cup-burner flames; (ii) calcium carbonate could not extinguish cup-burner flames; and (iii) the fire-suppression ability of calcium acetate was higher than that of ammonium dihydrogen phosphate, which was in turn higher than that of calcium hydroxide. Thermogravimetric analysis (TG) and X-ray diffraction measurements revealed that, although the calcium-compound powders decomposed and produced calcium oxide during flame extinction, significant differences existed among the fire inhibition efficiencies of the calcium compounds. TG and particle-size measurements proved that the high fire-suppression ability of calcium acetate resulted from the high ability of calcium acetate to generate inert gases during its decomposition, which diluted the oxygen concentration, thereby extinguishing the fires.