"They're all really dangerous stunts. We talk in parts about some of the people who have done these acts, and what has happened to them."
Tollemache said they had gone to great lengths to make sure they, and of course the audience, were out of harm's way.
"We never use audience volunteers.
"We've taken a lot of steps and trained for years to make sure that we're making it as safe as possible.
"But it's live - there's always a chance that something could go wrong."
It was what made the show so alluring, she said.
"I've never seen a crowd get so immediately engaged as when there is a genuine risk to the performer."
She said it was intoxicating but came at a cost. Both have been injured doing the stunts.
"We've burned and blistered our throats, our mouths and our fingers learning the fire stuff. And I've cut my feet open learning how to do the glass walk."
Ladderman said those experiences just inspired them to go back and train harder so it did not happen again.
Their hour-long show begins tomorrow night at the New Athenaeum, Dunedin, and finishes on Saturday.