Chicago, IL- Two teachers were hospitalized Friday morning, after they were sickened by a carbon monoxide leak at a Brighton Park neighborhood elementary school.

It happened at James Shields Elementary School, 4250 S. Rockwell St., around 8:30 a.m. – before any students were at the building, according to Fire Department spokesman Larry Langford.

“One of the engineers detected an issue, and he went to work on it right away, and literally kept the kids from coming in; stopped them at the door, and referred them to another building,” he said.

Langford said the school’s engineer quickly shut down the boiler after the leak was detected.

“They had some CO in the building. They then mitigated the circumstance, shut down the heating plant. The children were diverted to an annex building, so they were never inside; never had a problem with kids.”

Two teachers complained about feeling dizzy and were taken to Holy Cross Hospital in good condition.

Carbon monoxide levels in the building were unsafe, but not deadly, when firefighters arrived. The building has since been cleared of carbon monoxide.

The Chicago Public Schools have promised to install 5,000 more carbon monoxide detectors in school buildings by Dec. 1.

Less than a month ago, a gas leak at Prussing Elementary School sent about 80 students and staff to hospitals to be checked out.