A worker Murray Goulburn was taken to hospital suffering minor 'ice' burns and inhalation after ammonia leaked from a pipe that had been detached. The worker's condition is not serious.
CFA were called to attend the incident at around 6:40pm. Police, ambulance, worksafe and SES also attended the scene.
Operations Officer Peter Barr said there is no threat to the public and the situation is being monitored.
"CFA crews are taking readings and we will be closely monitoring the vapour levels," he said.
"This appears to be an unfortunate accident as the ammonia is normally isolated and not in the pipes during maintenance."
Up to 100 kilograms of ammonia liquid is estimated to have been in the pipe.
Mr Barr said ammonia is flammable and that emergency workers are expected to remain on site for a number of hours as a precaution.
"We will use special, safe fans to ventilate the area because once the cold ammonia liquid warms up it turns to gas and will rise into the atmosphere".