NSW RFS firies gather to remember 'Sando'

RFS commissioner Shane Fitzsimmons will join firefighters and volunteers to farewell "much-loved" colleague Paul Sanderson, who died of a heart attack while battling a blaze in the NSW Hunter region.

The 48-year-old Deputy Captain "Sando" was with fellow RFS volunteers taking refuge from a bushfire near Cessnock when he collapsed last week.

He was taken to John Hunter Hospital but could not be revived.

"It is a tragedy ... it is a sad day for us," a spokesman from NSW RFS told AAP on Friday, before the morning funeral.

"A great many volunteers and paid staff, including the commissioner, will be there today."

Mr Sanderson, a father of two and a grandfather, from the Kurri Kurri brigade, had been an RFS member for almost 20 years and was recently awarded life membership.

Commissioner Fitzsimmons said he would be greatly missed.

"It's absolutely tragic someone goes out for the want of nothing for free, to make a difference in their community and haven't been able to make it home," Mr Fitzsimmons said last week.

"The brigade will miss him, the community will miss him."

NSW RFS tweeted flags were flying at half mast at RFS buildings across the state.