The effect propane, methane, and a mixture of 18 vol % С3Н6–40 vol % С3Н8–42 vol % С4Н10 have on the combustion of air–acetylene mixtures is investigated experimentally. The upper concentration limit of flame propagation, maximum explosion pressure, and maximum rate of rise of explosion pressure are determined. It is found that propane and a mixture of 18 vol % С3Н6–40 vol % С3Н8–42 vol % С4Н10 are strong inhibitors of combustion of acetylene in its concentration ranges of 2–8 vol %. The inhibition effect becomes weaker as the acetylene content in the mixture increases. It disappears completely at C2H2 concentrations exceeding 15 vol %. The above experimental findings are explained using the proposed scheme of acetylene oxidation.