Brighton fireman Ben Melton is in training to complete six triathlons and six duathlons to raise money for children who have suffered from burns.
He aims to complete all 12 events this year and take part in an Iron Man Challenge in the middle of it all in the Swiss city of Zurich in July.
Mr Melton, 27, is raising funds for the Children’s Burns Trust.
He said: “I thought that the only way I am going to spread the word is if I do something close to what I do for my profession.
“If it were unrelated to the fire brigade it wouldn’t raise as much awareness.
“It has to be one of the worst things to have a fire in the home, let alone being injured in it and especially a child.
“This charity is close to my heart because it not only treats children who have suffered fire burns but also hot water scalds and all sorts of burns injuries.
“I have a nine-year-old boy myself and can only imagine how awful it would be to see your child suffer in this way.”
For each triathlon he will swim 1,500 metres, cycle 40km then run 10km.
The Iron Man Challenge involves swimming 2.4 miles, cycling 112 miles, then running a marathon.
Mr Melton will train every day and at peak times training will take up to five hours a day.
He will keep his friends and supporters up to speed with his progress on Twitter @Ben_CBT.
And he has set up a page on the Just Giving website at www.justgiving.co.uk/Ben-Melton to help him raise £1,000 for the London-based trust.