Fire and Emergency New Zealand Senior Station Officer Pete Brosnan, of Dunedin City station, said crews were called to a manual alarm activation at the Dunedin Hospital about 11.45am.
A crew was sent to investigate.
Information was received about a possible fire, SSO Brosnan said.
Because of the nature of the hospital building, further resources were dispatched.
Frederick St and Great King St were cordoned off while two floors were checked by firefighters.
It was believed the cause of the false alarm was fumes from maintenance work seeping through the building’s ventilation system, SSO Brosnan said.
A hospital spokeswoman said staff had smelt smoke on the fifth floor.
Staff who did not need to stay in the building were evacuated and no patients were endangered.
There was minimal disruption to service.
Hospital staff were grateful to firefighters for their quick response.