Dozens of shoppers and employees were asked to leave the Boscov department store in downtown Binghamton due to a state of smoke.
City firefighters responded to the four-story building at Court and Water streets shortly before 12:15 p.m. Tuesday.
A Boscov worker said he detected the smell of something electrical that could have burned.
Firefighters were first directed to the third floor for a smoky condition on the north end of the building.
Deputy Fire Chief Gerald Madden said it took some time to identify the source of the problem. He said the problem was traced to an overheated air handler. He said power to the unit was shut off and no damage was discovered.
Madden said there was no need for ventilation because smoke that may have been generated by the unit had dissipated by the time firefighters located the source.
Workers and customers entered the store around 12:50 p.m. Firefighters evacuated the premises 20 minutes later.