Bathurst Fire and Rescue NSW station officer Sandy Collins said a 75 millimetre street main was ruptured by a back hoe being used by a contractor on site.

Fire crews responded and two firefighters wore breathing apparatus as they sprayed a mist of water to dispense the gas cloud.

The water also offered fire protection to the gas company worker who was on site to stem the leak.

Station officer Collins said emergency services were called to the scene at 9.38am, with the situation contained just after 10am.

"The whole thing took less then one hour," he said.

"We were in the process of stopping traffic when the leak was stemmed, so traffic at the scene wasn't actually disrupted."