This is a fairly straightforward achievement. When you enter the church basement you will see quite a large number of furnaces creating somewhat of a maze around you. Each has the small word ‘blast’ in front of it, and if you keep your flashlight focused on them briefly, the furnace will release a small burst of fire. When going for this achievement, use the furnaces to your advantage against the waves of Taken you will encounter. They are a one-hit-kill for most of them. When you’ve killed every Taken, simply go around the room setting off the rest of the furnaces.