Since we have a Pyrotechnic in the group now, we have to deal with auras.
The text does not state whether or not a PC's aura can be turned off or if it's always on. The text gives the impression that all PC auras are on all the time.
I am going to rule that a PC's aura can be turned on or off with a minor action. Your aura is off unless you activate it by stating you are doing so. Once your aura is on, it affects all targets it's supposed to, in the Pyrotechnic's case, this is all creatures which means Enemies, NPCs, Allies, and other PCs.
Keep this in mind (I will try to do so as well) because it would not be good if you were burning your comrade to death while you were trying to stabilize him...