Putrescence

zombie surrounded by a cloud of putrescence

Clouds of putrescence are produced by zombies when they move or take damage. The gas will make you, or any other creature (including zombies themselves) nauseous. Because zombies produce this gas continuously, if you light one on fire they become a wandering ball of fire, burning everything they touch to the ground. Zombies can also be lit on fire when their gas comes in contact with a will-o-the-wisp, potentially destroying valuable resources as they wander.