Abstract. The effect of halide ions (X= Cl−, Br−, I−) on the kinetics of ozone decomposition by compositions supported on the natural bentonite of the Dashukovske deposit in Ukraine (N-Bent(D)) has been studied. It was shown that the activity of the KX/N-Bent(D) composition in the ozone decomposition reaction increases in the series KCl<<KBr<KI, but the complex composition K2PdCl4-Cu(NO3)2-KХ/N-Bent(D) demonstrates the maximum catalytic activity in the decomposition reaction in the presence of bromide ions. When the initial ozone concentration varied in the ozone-air mixture from 100 to 400 mg/m3, the reaction was first order for ozone at the beginning of the reaction (the first 10-15 min). The reaction order decreased in the stationary mode, which confirms the radical-chain reaction mechanism. It is shown that the bimetal composition K2PdCl4-Cu(NO3)2-KBr/N-Bent(D) demonstrates the longest protective action time (1800 min) at ozone concentration of 1 mg/m3.