A fire engine from Cosham Fire Station and two from Waterlooville Fire Station were called to the DPD parcel delivery centre in Dunsbury Park, Havant at 6.40pm on Monday.
The call was made after staff at the depot found ‘a white smokey mist’ coming from a package, according to a spokesman from Hampshire Fire and Rescue Service.
The package was revealed to be a container holding chilled horse semen, with the leaking gas coming from the liquid nitrogen used as a coolant, according to a spokesman from DPD.
Horse semen is often chilled to preserve it while it is being transported across the country to professional horse breeders.
Waterlooville Fire Station watch manager Craig Sadler said crews spent more than an hour there working to vent the gas.
He said: ‘It was a package that was leaking gas – it was a 30 litre vessel, stored in liquid nitrogen.
‘We evacuated the premises, with 15 people onsite.’
Two fire fighters in hazmat removed the vessel and co-ordinated a controlled venting outside, after confirming the gas was not toxic.
No one was injured.