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Next month, Glen Thurston (33), from Wanaka, and Erin Gray (32), from Queenstown, will join more than 1500 American firefighters to race up the 1311 steps of the 240m Columbia Tower in Seattle. Even though the building is not as high as the Sky Tower, because of the Auckland structure's 100m main antenna, their climb will be higher.
Both firefighters told the Otago Daily Times this week they were looking forward to carrying 25kg of breathing apparatus and firefighting clothing up the extra 208 steps.
They are members of a New Zealand team of 11.
While the 550 places in the Sky Tower climb usually fill in a day, all 1500 places in the Columbia Tower event are gone in 11 minutes.
Organiser of the Sky Tower event Tony Scott is an eight-time veteran of the Columbia Tower event and has a best time of 19min 1sec.
He believes Thurston is a ''15-minute man'', although the Columbia Tower record is less than 11 minutes.
Thurston, a Wanaka builder, who has been a volunteer firefighter for over three years, was sixth in last year's Sky Tower event.
Competitors must wear breathing apparatus throughout the stair climb and Mr Thurston says that means competitors must conserve air as best they can.
''If you go too fast, you puff more, you run out of air.''
And, he says, because of the restrictions of the breathing apparatus, competitors get fatigued very quickly.
''You can never really get a full lung-full, so it affects your muscle groups. It's a bit of a mind game, once you get moving.''
In the Columbia climb, competitors are assisted to change air bottles on the way up, in a scene Mr Scott likens to Formula One racing cars pulling into the pits.
Gray, a Queenstown lawyer and volunteer firefighter with five years' experience, won the women's section of the Sky Tower event in 2010 - with a back injury.
She has since had a back operation and is taking part in the Columbia Tower event to gain experience in preparation for the next Sky Tower event.
Competitors are sent off every 15 seconds and Ms Gray says overtaking in the narrow stairwell requires a certain technique.
''The approach I adopt is to smack people on the tank because ... you can't hear. All you can hear is your own breath.''
Both the Columbia and Sky events raise money for leukemia research
Tower climbs compared
Sky ... 1103
Columbia ... 1311
Sky ... 51
Columbia ... 69
Sky ... 190m
Columbia ... 240m
Sky ... 550
Columbia ... 1550
Sky ... 8min 43sec
Columbia ... 10min 53sec