Rural Fire Service Commissioner Shane Fitzsimmons said there was sadness right across the firefighting community following the death of the 48-year-old grandfather, who was a 20-year veteran of the service.

Mr Sanderson was helping to contain a five-hectare bushfire at Stanford Merthyr, near Cessnock, about 7pm on Thursday when he collapsed from a suspected heart attack, the Rural Fire Service (RFS) said.

Fellow firefighters tried to revive Mr Sanderson, who was the deputy captain of North Rothbury Fire Brigade, before paramedics took him to John Hunter Hospital, but he could not be saved.

"There is sadness right across the RFS community, right across the firefighting community," Commissioner Fitzsimmons said.

He said Mr Sanderson's family - including his mother, his wife Deena, children, and a grandson - were grief-stricken.

"Our thoughts and prayers are first and foremost with Deena, and the kids, and the family. They've lost a husband, a soulmate, and a grandfather. A mother has lost a son. That's the reality of what unfolded yesterday. It's tragic and it's sad," he said.

"The family is grief-stricken, but they're extraordinarily resilient.

"Together we need to help them get through this very difficult time.

"It's a sobering reminder ... of the volatile nature of firefighting and serving and protecting one's community."

Commissioner Fitzsimmons also praised the desperate efforts of Mr Sanderson's fellow volunteers in trying to save his life.

"The work they did on the fire ground in trying to revive him and save him was second to none," he said.