Chlorine leaks at a water treatment plant near an elementary school sent a firefighter, two plant workers and four children to the hospital Monday.

Sandy fire Capt. Todd Hyer remained hospitalized in fair condition Tuesday morning.The four children were at Lone Peak Elementary School, 11515 High Mesa Drive, when they were affected by chlorine gas that migrated from the leak.

The treatment plant, at 116th South and 25th East, is operated by the Salt Lake County Water Conservancy District and was being activated Monday after spending the winter in mothballs, said Battalion Chief Don Chase.

Chlorinators at the plant were activated at 7:30 a.m. A woman who lives near the plant was outside when she smelled the gas and called the fire department, Chase said. Firefighters from all three Sandy fire stations scrambled to the plant after getting the call at 9:19.

Chase said firefighters and plant officials believed the leak had been fixed when an alarm rang a second time at 11:05 a.m.

Hyer, plant manager James Carbine and Mike Winters, also a plant employee, were treated at Alta View Hospital after inhaling chlorine gas, Chase said. Winters was injured during the first leak.

Carbine and Winters had been wearing protective masks at other times during the morning but were not wearing them when they were injured by the leaks, Chase said.

All of the children treated at the hospital were sent back to school. State Health Department officials checked the school building for gas after the incident and found none, Chase said.

Firefighters and plant employees train together to handle this kind of accident, Chase said. "Their monitoring equipment is real good," he said. "We're confident we can handle anything up there."

Fire officials will check the chlorine system at the plant again before the equipment is activated, he said.