A major release of chlorine (Cl2) around 3:30 pm in a municipal swimming pool led to evacuating 40 people at the facility; 28 of them were examined onsite, including 4 children and the maintenance technician who were slightly intoxicated and required medical attention. The premises were ventilated; air samples and toxicity measurements were then taken. Since the analyses proved negative, the intervention concluded around 6 pm. The pool remained closed until the following Monday. The accident occurred during an inspection performed by a technician working with a private subcontractor subsequent to a technical problem involving a valve on the Cl2 dissolution device. The toxic gas dispersed into the air via the facility’s aeration/ventilation system.