It's a chemical mix that could kill.
“It can suffocate you and kill you. It's a pretty dangerous chemical that was created,” said Lt. Trent Zulick with the Reading Fire Department.
Firefighters and EMS worked quickly to save 20 people, including six kids, some as young as five, after authorities say a chlorine mix got messed up underneath the pool of the YMCA.
"Kind of double or triple or quadrupled the problem and that violent reaction creates chlorine gas,” said Deputy Chief Tom Kemery with the Reading Fire Department.
Symptoms hit swimmers.
"Irritated eyes, irritated throats,” said Zulick. “Kids had shortness of breath."
The sick got sent to Reading Hospital and St. Joe's, while first responders worked to get the gas out of the building.
"We set fans up, brought fresh air in,” Kemery. “We had to do a search to make sure nobody passed out."