He said cutting out sugar, carbs and his favourite meal - pasta - would no doubt help him get to the top faster. "For me, it's not about time. It's about making it. If I get under 20 minutes, I'll be really happy.
"My strategy will be to go slow and finish hard. But it might be go slow and go slow," he laughed.
Firefighters from 180 brigades and stations from around the country are participating and each person will be suited up in full firefighting gear, weighing 25kg.
More than $915,000 was raised last year.
Leukaemia & Blood Cancer NZ chief Pru Etcheverry said the fundraiser was a huge boost for the organisation and praised fire crews for their support over the years.
"We love their enthusiasm and are deeply appreciative of their dedication and support," she said.
Help support Nigel Morrison in his fundraising efforts.