Fire crews have contained a gas leak in a GNS lab in Lower Hutt.
Staff were evacuated from the building on Gracefield Road in Seaview as a precaution while fire crews decided if the gas should be vented or sealed.
GNS said a staff member noticed the leak of bromine pentafluoride and alerted the Fire Service just before midday.
The chemical, used in the analysis of rocks and minerals, was contained in an air-tight glass compartment.
The National Poison's centre said contact with bromine pentafluoride could burn skin and eyes and, if inhaled, could cause breathing difficulty and burn the throat.
It said it can also explode if it came into contact with water.
The Fire Service said Gracefield Road had been reoponed and people could travel through the area as normal.