The effects of ozone additions to natural gas/air mixtures on emissions of CO, C_nH_m, NO, and NO₂ were studied. The investigations have been realized in the stage composed of an ozone generator, the combustion chamber with a modified Mecker burner and gas composition, and flow rate and temperature measurement instrumentation. Comparisons were made of combustion with and without ozone additions. The tests were performed for 1.25 to 14.02 mg O₃/dm³(O₃+N₂) additions at 260, 330, and 390 W thermal powers and the air excess ratio of 0.8 to 1.4 using synthetic air. The investigations demanded the application of synthetic air. In experimental work a decrease of CO and C_nH_m concentrations with the ozone concentration in air and an increase in thermal power were confirmed and a slight increase of NO was observed. No effects of ozone on NO₂ concentrations have been detected.