A simple suggestion. When FIRE gets heated to 2499.85°C (according to wiki) it becomes PLSM. When PLSM goes lower than 2499.85°Cit still stays PLSM. Could you make it so when PLSMgoes below 2499.85°C it becomes FIRE?
This is unlikely to happen because of how much it would break. FIRE and PLSM are different things and none of the reactions were designed with this state change in mind. Anything that looks for FIRE would break when it's now PLSM instead.
(@RamenNoodlesGuy's example is good, because I don't have any specific reactions that would break at the moment, but that one definitely will)