A chlorine gas release in mid-March forced an evacuation at a medical rehabilitation facility in Middletown, a central Connecticut city about 15 miles south of Hartford, according to local officials.

The incident occurred at a physical rehabilitation center operated by Middlesex Health, where a therapy pool is used as part of patient treatment programs. Emergency crews were dispatched after staff reported a strong chemical odor inside the building.

According to fire officials, the release happened when incompatible pool chemicals were mixed, producing chlorine gas. The reaction prompted an immediate evacuation of the facility as firefighters and HAZMAT teams entered to isolate the source and secure the area.

At least one person was transported to a hospital for evaluation, while others were treated on site. Authorities described the injuries as non-lifethreatening.

Investigators later confirmed that the reaction originated inside the pool’s mechanical equipment room, not in the pool itself.

Air monitoring showed the contamination was largely contained to that space, though the building remained closed until it could be fully ventilated and cleared.

Preliminary findings indicate the incident was the result of human error during chemical handling, reportedly occurring during maintenance work.

When chlorine-based disinfectants come into contact with acids or other incompatible substances, they can rapidly release chlorine gas — a respiratory irritant capable of causing coughing, chest tightness, and more severe symptoms in enclosed environments.

Officials said the situation was brought under control within hours, and the facility was allowed to reopen after air quality testing confirmed safe conditions.