Opponents of the Mt Pleasant mine extension fear the project's environmental protection licence will be watered down to allow it to continue operating in windy conditions.
As part of its approval conditions, the commision has required the mine, located on the outskirts of Muswellbrook, to modify its operations during adverse weather events in order to minimise dust pollution.
It is a subtle but significant change to the mine's existing approval conditions that require it to cease operations on windy days.
"It has always been a sore point for MACH Energy - they were forced to stop operating when other mines didn't have to," Upper Hunter Air Quality Advisory Committee member Michael White said.
"They (the IPC) have softened the wording to make it consistent with other mines."
The mine's Environmental Protection Licence, a complementary document, still requires the mine to cease operating during adverse weather events.
MACH Energy declined to comment on the IPC's approval conditions.
The Newcastle Herald understands the Environment Protection Authority resisted pressure to remove the requirement to stop operating during windy weather when the mine's Environmental Protection Licence was recently reviewed.
Mr White, who previously managed Mt Arthur Coal, said he was concerned there would now be a push to make the Environmental Protection Licence align with the IPC conditions.
"They have effectively chopped the foundations out from under the Environmental Protection Licence," he said.
"We already have some of the worst air quality in Australia. There is no rationale in my view that justifies making it easier for them to pollute."
A Department of Planning spokesman said the applicant (MACH Energy) was required to meet both the consent conditions and the Environment Protection Licence.
"The air quality conditions set out by the IPC are in line with the recommendations from the department and are consistent with conditions imposed on similar mining projects," the spokesman said.
"They require the applicant to take all reasonable and feasible steps to minimise air quality impacts."
In its Statement of Reasons for Decision the IPC found the MACH Energy's application to extend the project's life by 22 years should be approved subject to a number of strict conditions.
These included a requirement for "air quality and noise impacts to be minimised, managed or at least compensated."
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