A chemical mishap at a Chicago children’s swim school triggered a hazmat response and sent several people to the hospital in late January.

The incident occurred during swim lessons and involved the accidental mixing of pool chemicals that released a harmful gas inside the building.

The incident occurred on January 29 at Goldfish Swim School, located in Park Ridge, Illinois, a suburb northwest of Chicago.

Emergency responders were called to the facility late that afternoon after staff unintentionally released chemicals in the building’s pump room during operations.

Fire crews arrived around 5 p.m. and quickly evacuated the facility while hazmat teams assessed the situation and ventilated the building. Authorities said there was no continuing risk to the public after the incident was contained.

Officials said the emergency began when pool chemicals were accidentally mixed, generating a gas inside the facility.

Park Ridge Deputy Fire Chief Derek Decker explained that the “initial investigation was a mix of chemicals that released a gas.”

Authorities did not publicly identify the exact chemicals involved.

According to fire officials, the chemical release was accidental and caused by an employee mistake while handling pool chemicals. The Park Ridge Fire Department said the event resulted from a “chemical situation” created by an employee’s error during operations at the facility.

Officials emphasized that there was “nothing suspicious at all at this point,” and the incident appeared to be an unintended chemical reaction rather than deliberate misconduct.

A total of 25 people were treated at the scene by emergency responders.

Those affected included students, swim instructors, parents, and staff members who were inside the facility during lessons.

Five people were transported to a hospital in nearby Park Ridge. Four were taken by ambulance, while one person later went to the hospital independently after leaving the scene. The people taken to the hospital were treated primarily for inhalation injuries and general illness complaints, according to fire officials.

Symptoms reported included breathing difficulties and irritation associated with inhaling chemical vapors. Authorities said all of the injuries were non-life-threatening, and those evaluated at the hospital were expected to recover.

Goldfish Swim School said staff immediately evacuated the building and notified emergency services. In a statement, the company said: “During afternoon swim lessons at Goldfish Swim School in Park Ridge on Thursday, January 29, 2026, the facility experienced a chemical release in the pump room. The Goldfish Swim School team acted quickly and followed safety protocols by immediately evacuating the facility and notifying the Park Ridge Fire Department.”

The swim school said it would continue supporting those affected and would work with local officials on plans to reopen safely.

Hazmat crews remained on site for several hours to ventilate the building and investigate the cause of the chemical reaction.

Officials said they were working to determine exactly what chemicals were mixed and how the release occurred.