Explanations for fire setting are easier to come by than explanations for fire resistance. Being able to set fires with nothing more than their hands, my 'fire-setters' need protection from the flames. So far, traits such as bony/keratinous plates or lots of protective skin would change the physique to something that appears less human. Perhaps symbiotic bacteria would work if there was a way to make the fire-setters not look furry with it. I'm mostly caught in a search for something at least slightly grounded in science.
How could my fire-setters have their skin and hair remain mostly undamaged in extreme heat?
Any kind of scientific explanation flies. Crazy diet, alien biochemistry, pretty much everything that works is fine with some explanation. As long as my fire-setters externally appear mostly human in shape, their skin and hair is reminiscent of humans', and they can maintain their fire resistance biologically. I don't mind at all if their abilities are limited, so long as they can at least withstand temperatures around 1,000 degrees Celsius (1,832°F) for at least an hour.
Don't worry about evolution, as these creatures are man-made. If this is too absurd and I should just hand wave, I understand.
Edit: Other requirements are that they think like humans and can fulfill basic requirements of living things such as having metabolisms, regulating themselves, and reproducing. I would prefer for them to have DNA and RNA unless this is impossible.