Investigation of a Chlorine Gas Release Caused by the Mixing of Incompatible Chemicals

摘要

This paper describes the investigation of a chlorine gas release at a public swimming pool. Over one hundred patrons were exposed to the chlorine gas release. The chlorine gas was generated by the inadvertent mixing of sodium hypochlorite solution and hydrochloric acid. The accident investigation concluded that the release was caused by a combination of maintenance and design errors. The maintenance error was procedural: on the second day of the maintenance task the contractor did not follow the standard lockout-tagout (LOTO) procedure for isolating the chemical feeder. If he had followed the LOTO procedure, the accident would have been prevented. The design defect was related to the control logic and the physical arrangement of the equipment under control. The causal factors of the accident are discussed and lessons learned are offered to prevent a recurrence of similar accidents. A key feature of this accident was the failure to properly isolate the automatic control system during routine maintenance.