Captain Fransen was tragically struck by a tree while fighting the fire.

Crew members immediately offered initial treatment until ambulance paramedics arrived. He was then transported to the Lightning Ridge health facility where he died.

Captain Fransen was part of a strike team that had been sent to the area from the Mid Coast and was on its first day of a three-day deployment. The team had been battling the fire in and around the small mining community of Glengarry.

RFS Commissioner Rob Rogers offered his condolences to Captain Fransen's family.

"Our thoughts are with his wife, Margaret and his daughter, Julia and son Paul and also the extended family," Commissioner Rogers said.

"I understand this obviously is a significant impact to not only his family but to the RFS itself. It's a very tight family-type unit, the RFS and these things are incredibly difficult for everybody involved.

"And we'll obviously be continuing to support Margaret and his family as best we can."

Commissioner Rogers said Captain Fransen was struck by a tree in the late afternoon and the local RFS crew did "everything they could to support him in his condition until paramedics could arrive".

"The paramedics worked tirelessly to try and save him," he said.

Captain Fransen was a life member of the Diamond Beach brigade, which is on the state's mid coast, not far from Taree.

He joined the brigade in 2010 and has held many roles within the brigade, but mostly recently, he was made the captain of that brigade.

"He was a very active member of the RFS," Commissioner Rogers said.

NSW RFS wrote on its Facebook page: "His passing will be deeply felt across the RFS, but Leo's ultimate sacrifice demonstrates the daily risks faced by our firefighters. He will continue to inspire his fellow members and form part of our enduring memory."

The Hudson Fire began on November 12 from what the RS believes was a lightning strike.

It has burnt more than 21,000 hectares, destroyed 66 buildings and "there's still more work to do to try and bring that fire under control", Commissioner Rogers said.

IN OTHER NEWS: