Staff and visitors were evacuated from the building, with three pumpers, two commanders, the Breathing Apparatus Support vehicle, the Bronto and a HAZMAT truck on scene.

Deputy Director Kirsten Paisley said there was a small fire in the gallery's workshop.

"The situation is under control and at no stage was there any risk to people or the collection," she said.

"All public and staff were evacuated calmly and quickly. However as a precaution, the building will remain closed for rest of the afternoon.

"It will reopen to visitors tomorrow morning as usual."

In a statement, the ACT Emergency Services Agency said firefighters were cutting open the ducting to ensure the fire was fully extinguished.

A build-up of saw dust from a machine caused the fire to start in a workshop at the back of the gallery.

The cause is not suspicious.