ACT Fire & Rescue are inspecting a science room filled with mist at the Australian National University.
Crews say the mist is a combination of helium and nitrogen.
It’s believed the gases may have been leftover from experiments.
An alarm system was triggered at 00:42am.
Three pumpers, the Hazardous Materials Unit, Breathing Apparatus Van and two commanders are on scene at North Road.
Update to follow.
Crews have begun leaving the scene but the area will remain cordoned off.
There was no danger of fire or explosion and the gases in the science lab were vented by the Hazardous Materials Unit.
ACT Fire & Rescue have handed the room over to ANU authorities, who will continue investigations this morning.
The Hazardous Materials Unit and a pumper are expected to return to the scene at 8:30am to conduct final atmospheric testing.