When you enter the basement, you’ll notice the entire basement is filled with furnaces with the word “blast” around it. Shine your flashlight to make each of the furnaces blast. The basement is very dark and maze-like, and can get confusing if you manage to lose track of which ones you’ve done. Once you shine your light on them, they'll create a flashbang-like blast that's very bright. Some of them may blow up another furnace across from them. If this happens, make sure you go check to see if you missed any. When you manage to kill all of the Taken in the basement, go back and check to make sure that you got them all. The achievement will unlock when you blast the last one.