Heidi Cannon, a machine operator for a Mornington Peninsula chicken company, was fired for showing up to work at a farm after drinking wine during the day on November 4 last year.

She fell asleep during her midnight-7am shift and accidentally caused up to 50 chickens to be "smothered" to death, the Fair Work Commission heard.

Ms Cannon claimed her earlier alcohol consumption of up to five glasses of wine meant she was unable to drive to the Ripplebrook farm, but she believed she was sober enough to work and operate the machinery.

Fair Work Commissioner Nick Wilson asked Ms Cannon how she could have thought she was able to work in the knowledge she was intoxicated and unfit to drive

But Ms Cannon denied being drunk, saying she did not want to take the risk driving because she could have been breathalysed. "I would have had it [alcohol] on my breath still, which could make me over .05," she said.

The tribunal heard that her boss, Matteo Geminian, was called to the farm about 3am by another worker, who claimed Ms Cannon was "useless", saying she was intoxicated and had fallen asleep in a truck.

"Heidi wasn't in the shed doing what she was supposed to do," the worker allegedly told their boss, "so 50 or 60 birds got run over or smothered."

Mr Geminian told Ms Cannon she was fired some time after 3am on November 5 over the phone, and then at 3.45am when he arrived at the farm and smelt alcohol on her breath, the tribunal was told.

The employer, Poultry Harvesting, argued that Ms Cannon was intoxicated and could cause "serious and imminent" health and safety risks.

But it was ruled that Mr Geminian had insufficient knowledge about Ms Cannon's condition to have formed the view she was intoxicated and took no steps to objectively assess her condition. Ms Cannon was also not provided with an opportunity to respond to the allegations against her.

The tribunal rejected Poultry Harvesting's argument that Ms Cannon neglected her duty during work hours by being "passed out in the truck", with the company unable to counter Ms Cannon's testimony that sleeping on the job was commonplace when trucks did not arrive on time.

There was insufficient evidence to show that Ms Cannon was bound to a "zero-tolerance" alcohol policy at work, the tribunal found.

"It is possible to form the view that, like many workplaces, those attended by Poultry Harvesting employees in the course of their employment require workers not to be intoxicated ... however the evidence does not permit a finding that Ms Cannon was bound to a zero-tolerance policy."

Poultry Harvesting was ordered to pay Ms Cannon $7000 in compensation plus superannuation.