Hazards caused by detonation of hydrocarbon-air mixtures are a continuing problem. Of the factors affecting detonation hazards of hydrocarbon-air mixtures, additives play an important role. In this paper, a series of experiments are described addressing the influence of chemical additives on the detonation of some hydrocarbon-air mixtures under confined (rectangle shock tube tests) conditions. The experimental results show that NT (nitric ether or RONO2), PO (1,2-epoxypropane), and BPO (benzoyl peroxide) have a clear sensitizing effect on the detonation hazards of these mixtures. The mechanistic influence of additives is simply described, according to the chain reaction theory of detonation.