"If you die to this impulse, you return to life at the start of your next turn in the same space. When you return, you have Hit Points equal to double your level." pg.21
By the time you gain this 18th level feat, you have Elemental Immunity at 17th, "Your elemental resistance becomes full immunity. While you have an element gathered, you’re immune to effects with that trait; you can voluntarily allow them to affect you." pg.8
And don't think the Overflow trait will remove this immunity as it states, "When you use an impulse that has the overflow trait, any element you have gathered disappears after your action." pg.4
Granted, one could voluntarily allow ASEiF to affect you but at that point you are also a master in Reflex saves and get a critical success on a success so it's quite unlikely to kill you since in PF2e, you cannot voluntarily fail saves unless an effect specifies otherwise.