Complex sentence: Bart also remembered that Bob insisted on getting a room with a fireplace, which convinced him that Bob was interested in the gas used to light the fireplace, since fire ignites and can generates an explosion when it mixes with enough gas.
Split into simpler sentences: Bart also remembered that Bob insisted on getting a room with a fireplace, which convinced him that Bob was interested in the gas used to light the fireplace. Fire ignites and can generates an explosion when it mixes with enough gas.