"My first thing is usually it's either a drill or a child who's pulled the fire alarm, that occasionally happens," said Mikeal Doyle, a YMCA employee.
But this wasn't a drill. Investigators say there was a hazardous chlorine release around the indoor pool.
"It can create respiratory difficulty and cause the respiratory system to shut down. It can also cause fires, something that wouldn't normally burn under normal conditions," said Yakima Fire Shift Commander Mitch Cole.
Investigators say a maintenance worker was mixing chlorine tablets for the pool when he noticed a strong fume and unusual bubbling. That's when he called 911.
It was serious enough to call in Hazmat. The quick response kept anyone from getting hurt.
"It did work out well, everything seems to be okay and everybody got out safely and that's what's the most important of all," said Mikeal.
The YMCA thinks the bad reaction happened because the chlorine tablets were made by two different companies and shouldn't have been mixed together. A mistake it won't make again.
"The biggest thing then is just making sure that you take care of whatever the issue is, figure out what happened and make sure you don't have it repeated," said Bob Romero, the executive director of the Yakima YMCA.
Employees with the department of Ecology removed the chemicals. Authorities aired out the building and tested it to make sure it was safe before letting anyone back inside.
The Y was back open by noon.
There were about 60 kids at the YMCA for summer camp. They're between five and 12 years old and had no ill effects. The maintenance worker who mixed the chlorine initially reported some breathing problems. But, he checked out fine at the scene.