Burning is a process in OE-Cake. This makes random pieces of Fire or Powder (or any material with Fuel or Powder+Hot mixed into it) disappear over time. The rate at which Fire Decay occurs can be modified in the Parameters under the variable fireExtinguishProbability, which determines how long each particle lasts before it dies. There seems to be a glitch that simulates "heat" because burning particles in contact with other burning particles die faster than if they are on their own. Objects containing Fuel + Hot or Jet + Hot will produce the Fire animation.