Two New South Wales firefighters who were trapped inside their burning trucks during a terrifying ember attack on the state's South Coast on Tuesday say they are amazed everyone came out alive.

Four crews were on their way to help with the Currowan bushfire and were just south of Nowra when they were caught in a "flashover" and quickly became surrounded by flames.

Deputy Captain Jasper Croft from Station 509 Wyoming said when his truck lit up, the heat was "intense".

"Everything was alight, both sides of the truck, the top — everything," Mr Croft said.

"It was like being in an oven,"

Firefighters Deputy Captain Jasper Croft and Kayle Barton were trapped inside their burning trucks during a terrifying ember attack. ( ABC News: Talissa Siganto )

Mr Croft said there were moments he did not think his crew would make it.

"When we were in the thick of it we thought this could be it … It was pretty traumatic" he said.

Mr Croft was among 16 firefighters who managed to escape their burning trucks and retreat to safety.

Kayle Barton, who was in another truck which seized and trapped his crew, said he was determined to get everyone out alive.

"My first thought was this is not happening … This is not going to be our last moment," he said.

Mr Barton said their training "kicked in" and they were able to get out unharmed but their truck was destroyed.

One firefighter said being inside the burning truck was like being inside an oven. ( Supplied: Fire and Rescue New South Wales )

"Every piece of equipment worked exactly as it was intended … Everything worked," he said

"We're all amazed.

"Trucks can be replaced … Our crew managed to get out, that's the most important thing," he said.

Fire and Rescue NSW Deputy Commissioner Jeremy Fewtrell said he was "incredibly proud" of the men and thankful they got home safe.

"We were aware of the situation they were in … Collectively, the whole organisation breathed a very large sigh of relief when they managed to get themselves out," he said.

"The manner in which they got themselves out is a tribute to their professionalism and their capability, great skills but also great presence of mind under incredible pressure."

"It reflects incredibly well on their training and the equipment that they had to keep them safe," he said.

The mammoth blaze is almost 230,000 hectares large and has been burning in the Shoalhaven area for more than a month.