About 150 people were evacuated from the Bank Centre building in Nathan Road, Mongkok, yesterday after a toxic gas leak.
Fire officers said workers in the building reported an odd smell emanating from the air-conditioning system at about 1 pm.
The gas was identified as Freon 22, which can cause suffocation.
The top eight floors of the 24-storey building were evacuated and officers traced the leak to the air-conditioning machine room on the top floor. No casualties were reported and workers were allowed to return to the building when the gas dissipated at about 2.30 pm.
A senior government chemist said the gas had a 'low toxicity' but could cause suffocation in an enclosed space.
Dr Louis Leung Man-lay, of the Baptist University's Department of Chemistry, said Freon was a common industrial chemical.
