Hey Chris,
workers in high temp. conditions have been carrying Zippos for years for that very reason, butane explodes all at once, but the fuel in Zippos leaks off and dissipates before igniting, it can still cause a nasty contact burn (skin irritation), but it doesn't blow your leg off. I don't know how hot it would have to get to get one of these to explode, but I would guess (with VERY high confidence) that it would be well beyond the point of endurance of the human body. I do know though, of three persons in the last 30 years that, while working at a glass plant, bacame permenantly disabled due to carrying butanes. It's now a firing offence to be caught with a butane lighter on the hot line at Owens-Brockway, but Zippos and their knock-offs are OK to have, that alone's got to tell you something.
Troy