Back with the C-4, Desmond explains the BOOM

Back with the large amount of C-4, Desmond examines the set-up, stating that he had 6 months of explosive ordinance disposal in the military, which he says is just enough time to get yourself blown up. He explains that there's a trip wire (screen 5), dummy wiring (screen 6), multiple fire systems (screen 7) and battery (screen 8) and if any of these are disconnected or deactivated that there will be a BOOM.

It's an a elaborate setup. To read about the unpractical nature of this bomb, read Adam Savage from Mythbusters statement here.