The Propane Tank is an usable item in Call of Duty: Ghosts, Extinction mode. It is very common and can be picked up and thrown. When shot at, the propane tank will explode, causing a large explosion able to kill scouts and scorpions. A good strategy with them is to put one next to a flare, and blow it up while a large group of Cryptids are distracted. They can also be thrown on barrier hives and blown up to do additional damage to destroy it faster (damage only applies once the helicopter arrives and starts firing on it)
Oddly, having multiple tanks in the same area and exploding them simultaneously will only do the same amount of damage compared to a single tank, but with a larger explosive radius. This can be seen when using multiple tanks in one go on a barrier hive, and the health bar only loses 1 tanks worth of health. This has since been patched, so more damage is dealt with more tanks, but putting them on indivdually still yields more damage.