Plans are being made to evacuate Morwell, but the smoke cloaking the Victorian town is still a long way off levels needed to trigger an evacuation, the state's chief health officer says.
Morwell locals are in shock that the fire which spread to the Hazelwood open-cut coal mine on February 9, sending thick smoke into the town of more than 13,000 people, was deliberately lit.
"I cannot understand what you gain through doing something as terrible as that to affect so many people's lives," resident Andrea Camier, who lives within a kilometre of the fire, told AAP.
Chief Health Officer Dr Rosemary Lester said an evacuation plan is being prepared for Morwell and carbon monoxide levels are constantly being monitored.
But the impact from smoke is "nowhere near" the level required to evacuate the town.
"We don't believe there's a necessity to evacuate," Dr Lester told reporters in nearby Traralgon.
"We haven't seen levels rise to anywhere near a level where we would be concerned."
The Environment Protection Authority issued a high level smoke alert for the Latrobe Valley on Wednesday.
Authorities have given 25,000 face masks to residents but Dr Lester says there's no evidence of long-term health effects from a short-term exposure to smoke and ash.
A union says a paramedic feared she was having a stroke after becoming unwell while attending the mine fire, suffering chest pain and shortness of breath.
Crews are hoping to have the blaze put out in two weeks but Fire Services Commissioner Craig Lapsley concedes it could be months if conditions are not favourable.
High temperatures and winds forecast next Thursday could create severe fire danger, posing another challenge for them, he said.
Mr Lapsley was also concerned the fire fight could cause a landslide at the mine.
"The fact is that as we put water in, we potentially erode parts of it. That's a key consideration for our people," he said.
"We do not want a landslide in that mine."
Police are hunting a calculated arsonist who sparked the fire.
Sharon Dale, who works in Morwell, said she was appalled to learn a firebug was at work.
"It's just disgusting. There's so many people sick from it now, and the smoke and the fumes. It's just really bad.
"It's the smell of the coal that's the worst thing."
Morwell resident Howard Williams says locals believe they know who the firebug is.
"But there's a big difference between that and having enough evidence to take action."