About 100 people were evacuated from the Royal Australian Mint on Wednesday morning after gas triggered the fire alarm.
ACT Fire and Rescue responded to the alarm about 10am, which they said was triggered by the "release of gas through a chemical reaction" at the Deakin coin factory.
ACT Ambulance Service attended to one person at the scene, but they did not need to be transported to hospital.
The building has been declared safe after HAZMAT crews conducted atmospheric monitoring and air ventilation testing.
The Royal Australian Mint said it could not provide any further information on the cause of incident when contacted by Fairfax Media.