"Volunteers are struggling in communities because young people have so many other things happening in their lives," he said.
"I look around this room and everyone is in the upper middle age.
"Young people have a lot of skills but getting them over the threshold to volunteer is hard."
Mr McNabb, who trained Dannevirke's volunteer firefighters when working for the regional fire service, said our brigade is a "dedicated bunch."
"The Dannevirke brigade is fantastic with some extremely dedicated people," he said.
"Fire chief Pete Sinclair is a natural leader and a brilliant guy, as is former chief and now fire investigator Mike Finuncane."
In 1980 Mr McNabb worked on oil rigs in the North Sea off Scotland.
"We were 300 miles out at sea on a piece of steel and I was a firefighter helicopter crewman," he told the Dannevirke News.
"In 1987 I returned to New Zealand and the Nuhaka Fire Brigade and was a volunteer firefighter for nine years.
"I then spent 11 years at the Fire Service's regional headquarters in Hastings and became a national instructor."
Mr McNabb left the Fire Service seven years ago and now works in a private capacity training rescue teams for Fonterra and Silver Fern Farms and other companies, as well as working with the Tararua's rural fire crews.
On Sunday he gave the Fantasy Cave volunteers an insight into fire safety.
"It's about keeping it real because a lot of people have a false idea of fires from what they've seen on television," he said.
"Evacuating people is like herding cats and you guys have to have eyes in the back of your heads.
"In the 1950s you had 11 minutes to get out of your home in a fire, now it's two minutes, because of all the highly inflammable material and an average house fire, free-burning, will double itself every 90 seconds."
Mr McNabb has offered to run a day-long basic first aid and fire extinguisher course for the Fantasy Cave volunteers.
"I want to be involved because I've seen what you guys do and it's fantastic," he said.
Tararua District mayor Roly Ellis also acknowledged the work of the volunteers.
"The cave is a great thing for Dannevirke. I realise many of you are getting older but there are always people retiring so all you need to do is grab them."