TNT is detonated from being lit on fire (such as from a Flint and Steel ) or from receiving an active redstone current. When using TNT in a redstone circuit it doubles the capacitance over a repeater. There is a 4 seconds fuse time, allowing the player to retreat to a safe distance. After being ignited, it will perform a slight jump in the air before returning to the ground. It will flash white for exactly four seconds and allow the player to move through it, exploding soon afterwards.