Potentially hazardous releases due to chlorine gas leaks have been a crucial social issue in Taiwan, especially leaks that have occurred in the process plants in general, such as water treatment plants (WTPs), petrifaction, and so on. Classified as a highly toxic gas, chlorine presents severe hazards when contacting the human body in various ways. It can very easily enter the human body through the skin, the eyes, inhalation, or by being ingested. Environmental contact typically affects the eyes, trachea, and respiratory system. In process plants, the units for transferring the chlorine gas are relatively effective and complex, including steel chlorine cylinders, piping, valves, and chlorine addition equipment. This study shows the benefits of developing an adequate emergency response plan (ERP) with safety and industrial hygiene resources to deal with the effects resulting from a chlorine gas leak, in order to lessen or avoid injury to plant personnel and citizens in the neighboring community. Results from systematic planning indicate that properly trained personnel could immediately and effectively handle each level of incidents occurring in the process plants in Taiwan. (C) 2008 Elsevier Ltd. All rights reserved.