Rocky Hill High School students are being dismissed for the day after an oil line separated from a malfunctioning air compressor, sending heavy smoke into the basement.
The fire department responded and pumped water into sprinkler system, but sprinklers never needed to activate because there was no fire.
However, smoke filled the basement, first and second floors.
Students were moved to the football field and are now being sent home.
A firefighter also had to be transported to the hospital to be treated for a leg injury.