that he might actually die in a tunnel collapse ; that one misstep might send him hurtling down a hidden escape shaft or forgotten blasthole to bust on the rocks like a blood balloon or , even worse , only break his legs so that he died from thirst slowly and in great pain ; that given the right conditions , a tunnel could flood in a few minutes and much faster than any kid could run ; that a person could keel over from swamp gas and suffocate before he knew what hit him-all that danger added to the thrill .