The effects of reaction temperatures, reactor materials, addition of TiO₂, and irradiation of UV on the PVC sample on the dehydrochlorination reaction were studied in the continuous tubular reactor. The extent of reaction was measured with the changes in pH due to the evolution of HCl, which is the most sensitive method ever. The autocatalytic effect of HCl was observed in all experiments. Reaction rates were fitted with two parameter models which include the induction time and the degree of autocatalysis (n). For the first time, branched chain radical mechanism was proposed to explain the autocatalytic effect of HCl. As the reaction temperature increased, n increased. In the case of Fe sample holder, the promoting effect of Fe was observed. The addition of TiO₂ into PVC sample increased reaction rate and n.