Middlemarch volunteer brigade members Audry Julien and Kiera Watson-O’Neill spent the day walking on a treadmill in the "stinking" hot sun outside the New World supermarket in Mosgiel.
They did it to raise funds and awareness for fighting leukaemia and blood cancer.
They began the challenge at 8am.
Mr Julien said it was a hot day and both of them were feeling it even more because they were wearing their full firefighter outfits.
Nonetheless, both were in good spirits and thinking positively.
"Hopefully, as the day gets hotter and we start to sweat more, people feel sorry for us and donate more."
They were stocked up on water and motivated to go the whole way.
Their strategy was to take turns walking on the treadmill and to switch every hour to begin with and then switch every half an hour when it started getting tougher.
Mr Julien said the fundraiser was a part of the Firefighter Sky Tower Challenge that he and Miss Watson-O’Neill would be taking part in on May 24.
They would be racing other firefighters from across New Zealand and trying to climb about 50 floors of Auckland’s Sky Tower the fastest.
Last year, Mr Julien did it in just over 14 minutes and this year he was hoping to complete it in 12 minutes.
The pair were attempting to raise $3400 for the challenge.
