Victoria's Fire Services Commissioner Craig Lapsley is concerned that forecast hot and windy weather next week will exacerbate efforts to control the Morwell mine fire.

The fire in the open cut mine has been burning for more than two weeks, sending choking smoke over the town of Morwell and causing health problems for local residents.

The fire escaped from the mine on Tuesday and came within metres of the Hazelwood power station, in hot and windy weather.

But fire crews managed to stop it before it damaged the station, although power output was temporarily reduced.

Commissioner Lapsley says with over 200 firefighters working on the blaze every shift, they have managed to reduced the size of the fire by 50 per cent.

But he concedes without heavy rain, the fire could burn for months.

"It's got the potential to do that (burn for months). The best case scenario is 14 days," he said.

"Let's be realistic... We're putting the resources in, the work plan is there to get a 14-day containment strategy around it."

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He says the weather may be conspiring against them.

"Remember we've got weather next Wednesday and Thursday, bringing in high winds and temperatures. That will challenge us," he said.

Chief health officer Rosemary Lester says an evacuation plan has been prepared in case Morwell residents have to be moved but carbon monoxide levels in the town would have to rise to worrying levels.

"We need to look at a particular level over a period of exposure before we would need to think about evacuation," she said.

"We are constantly monitoring that and we haven't gone anywhere near what we would regard a level to trigger talk about evacuation."

Victoria Police and Ambulance Victoria have told female officers who are either pregnant or wanting to become pregnant not to work at the fire staging ground because of the exposure to carbon monoxide.

Dr Lester says those at the mine are being constantly monitored for carbon monoxide exposure but it is a different situation in town.

"For people in the general Morwell community, carbon monoxide is being constantly monitored across the town and we haven't seen any levels of concern," she said.

Smoke rising from burning coal face at Hazelwood open cut mine. ( ABC Graphics )

"So there's no need for pregnant women in the town of Morwell to be concerned."

Dr Lester says they know short term exposure causes some health problems for people with pre-existing illnesses but after burning for three weeks, they still have no definition of what long term exposure is.

"Although in the scheme of things it has been very distressing to live through, at this stage this is still regarded as a short term exposure," she said.

"There is no evidence of any long term health effects from this sort of smoke and ash for this type of short term exposure."

Local residents are planning a protest on Sunday and say they expect hundreds of people to attend.