Firefighters are conducting ventilation operations at the Canberra Outlet Centre after responding to a gas leak.
A battery overheated on cleaning equipment in a cupboard near the main entrance and caused the gas.
Crews are working to make the area safe.
ACT Fire & Rescue was alerted to the incident in Fyshwick by an Automatic Fire Alarm at 6am.
Two pumpers, the hazardous materials unit, the breathing apparatus van and a commander are on scene.
It is estimated units will remain scene for about an hour.