Odd concept: fire for blood

[ScaryMJDiamcreep]

I've got a character concept for a person whose blood is made of fire, but I'm struggling to think of ways to do it so that their body isn't damaged by their blood. The main way that I've got at the moment is that they've got some kind of chemical in their blood that reacts to the air, but only under the lower pressures found when outside the body. But I can't think of any real chemical like that, and I'm not sure whether my grasp on how that would work is even correct.

 

[FifthView]

Phosphorous ignites when exposed to air.

Here's a link that might help: Pyrophoricity - Wikipedia

How you could possibly work this is....up in the air for me. But who knows?

 

[ScaryMJDiamcreep]

The problem with the substances listed on that wiki page is that none of them look like ones that would be unresponsive to the amounts of air that would be found within the blood.

 

[CupofJoe]

If this is for a fantasy story, then why does it have to be real? Invent a compound or an element that is unique to your world. I didn't think Avatar was less of a film because they were [literally] mining Unobtainium. I did think it was a really stupid name though.
As for why fire for blood might be possible, make it a blessing or a curse, the "gift" of a god or the side effect of another magic...

 

[ScaryMJDiamcreep]

Curse sounds about perfect for the character I had in mind, though now I've got to come up with a when, where, how and why the curse was placed. Got an idea for the majority of the why, but that on it's own seems a bit lacking, cause otherwise all people with that type of magic would have fire blood, and I want that to either be a thing unique to that character, or a curse on the character's whole bloodline. Pun not intended.

 

[K.S. Crooks]

A curse from a higher being is a common way. It could be an ancestor of your character dabbled with forces of nature and created a unique condition that resulted in the fire-blood and their altered physiology. Perhaps thinking of the benefits and detriments having fire-blood gives the person may help you figure out how it was originally created.