A fire broke out at the National Archives of Australia's preservation facility in Mitchell in the early hours of Monday morning.
The blaze started in a dehumidifier unit just after 4am on Monday.
No items being preserved at the National Archives building were damaged in the incident and no one was inside the building at the time.
Multiple fire crews were called to the scene and quickly extinguished the fire.
An ACT Emergency Services Agency spokeswoman said the building was, however, heavily smoke logged.
Crews took several hours to ventilate the building and clear the smoke.
The spokeswoman said only the dehumidifier was damaged in the fire and all other items were safe.
Firefighters handed back the building to staff just after 9am.
It's expected the building will be operational again later on Monday afternoon.
