The BruceG 15

To unlock this achievement you simply need to be able to kill a least three zombies with a propane tank. This can be done in a couple of ways. You can use a portable tank, place it in the street, next attract a horde and shoot the tank as they approach. Another alternative is to find a house with a detached garage. Some of these garages or house in the farmlands have large stationary propane tanks next to the garage. Run up to the building to get the attention of the zombies inside, start to back peddle as the zombies start to parade out of the structure, and as they pass the tank shoot it to unlock the achievement.