"There's a changeover at the 42nd floor and there you feel the burn but you know you're near the top. You have to start digging in to get there."
Last year Mr Osborne reached the top in 22 minutes. The fastest that year was Aucklander Josh Harrison in 8 minutes and 37 seconds. Mr Osborne said volunteer firefighter Clay Gulliver was his pick to be fastest from the Rotorua firefighters in under 14 minutes.
The firefighters have been training since December with stair repeats at the Arawa Racecourse grandstand, the Quarry Track in the Redwoods and climbing up the Jubilee Track on Mount Ngongotaha.
Mr Osborne said he had also been cycling and running to build his fitness for the event, which they complete in full firefighting gear including breathing apparatus.
"It's a matter of regulating your breathing and trying to keep it under control," he said.
Mr Osborne said the Ngongotaha station hoped to make it an annual event but with only 700 spots available this year's sold out in 10 minutes. The crew has raised about $5000 for the charity.
This is the first time Lake Okareka Rural Fire have signed up.
"It is very different for us as rural firefighters to be all suited up for an indoor event like running up 1103 steps - we usually fight fires across the wide open land, and in the forests," said volunteer Blair Gilbert.
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