The 362,117 hectare blaze, which was increased to 'watch and act' late Thursday afternoon, is now back at 'advice' level.

At 10pm on Thursday the fire was burning within five kilometres from Angus Place Colliery on Wolgan Road.

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"The area is extremely smokey with visibility down to around 500 metres or less," NSW Rural Fire Service (RFS) Chifley/Lithgow district assistant Michael Dunn said.

"Residents moving around in the area should proceed with caution."

Aircraft will be used on Friday to help firefighters assess the fire's behaviour.

Mr Dunn said the strategy during coming days would be to continue back-burning operations heading west towards Clarence in order to strengthen the containment line.

"There are a number of pre-identified triggers that the planning team have in place to ensure that the works are carried out in advance of the fire advancing towards Bells Line of Road," he said.

"Areas burnt during the 2013 State Mine Fire are also providing some advantage by slowing fire progression."

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Mr Dunn said higher humidity is slowing the back burns progress in this area, however this will also slow the southward movement of the fire edge.

"People in the communities along Bells Line of Road should expect to see an increase in fire activity as a result of the back burning operations," he said.

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"Additional back burning will commence around the villages of Clarence and Dargan to create a containment line for the fire moving across from Newnes State Forest."

These operations will be ongoing as conditions allow.

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