Incompatible chemicals accidentally mixed at an Ohio YMCA sent three people to the hospital and prompted a large emergency response.

TheYMCA,locatedinYoungstown, was in the midst of receiving a delivery of swimming pool chemicals when, according to Battalion Chief Chad Manchester of the Youngstown Fire Department, some aluminum sulfate was inadvertently mixed into a chlorine tank, producing chlorine gas.

“When the two chemicals got mixed together, it was pretty serious because it caused an inhalation hazard that did spread a little bit through the building,” Manchester said.

Suffering from minor breathing problems, two people were taken to the hospital by the Y’s CEO, and a third person was transported by ambulance.

A fourth person was checked outside the building but did not require further attention.

The fire department and Hazmat teams arrived after the building was evacuated and cleaned up the spilled chemicals to make sure there was no more chance of a reaction.

“The Hazmat team is very good at what they do. They’ve done considerable research on the chemicals that were mixed together. They’re going in in suits that will protect them and were able to neutralize the materials,” Manchester said.

The YMCA was closed for the day.