Introduction: Today, with development of various industries, the adverse events originated from explosion and emission of toxic and chemical substances have increased. These events may cause serious environmental problems that threaten human health and safety. Therefore, knowledge about the risk of toxic substances from industrial facilities is essential. Although, chlorine is extensively utilized in water treatment as a disinfectant and some chemical processes as an oxidizing agent, it can lead to some concerns in environmental issues.

Materials and methods: In this study, distribution of chlorine in the water supply of Eyvan city from Ilam province, Iran, and its surrounding areas is evaluated and high-risk regions are defined by Process Hazard Analysis Software Tool (PHAST) specialized software.

Results: The modeling results showed that the cloud of chlorine is about 1220 m across just downwind of the release for the first scenario (rupture of a chlorine vessel) in the summer; however, the probability of fatality is 100 % in a whole year in a distance of 40 m from the vessel. For the second scenario (rupture of pipeline including the chlorine gas) the human death mostly occurs in a distance of 25 m from the pipeline with the probability of 2.8 % in the summer due to low rate of released gas.

Conclusion: As an important result, the land around the chlorination unit covering a distance of approximately 1220 m is vulnerable and risk prevention in that region should be accounted for.