Narrator:
Yet more reasons I take something for my absentmindedness... the mitigated part barely seems there. Lets see if I can get to everyone this afternoon.
Well... technically it's fireproof... based on a
RAW interpretation only when protecting the wearer from a skill failure while extracting (frex) the fire glands from a Salamander (or like any fire breathing/exhuding creature).
Since that's primarily what it's meant for, protecting the wearer from their own Alchemy and Organ Harvesting (and probably Hazardous Materials (Biological/Chemical)) skill failures.
Jareth's garb/armor was 'given the treatment' mostly to protect it from the sewers... and to make it easier to clean should he fall in something nasty.