Note: Michael.
Not to discredit your knowledge in the areas of heat chemistry, or overexaggerate mine.
Simple radiated heat could not allow a person to spontaneously combust. The yellowing of the walls would not be caused by radiation - but an enormous amount of heat on the other side of the wall - causing it to glow due to atomic vibration - and pressure, which is the only reason why the wall hasn't melted yet. True - If you were to touch, or come into contact with the wall, your hand would blister, at least - if not catch like a faggot. However, I agree that a blue glowy room would be awesomely deadly. Unless there's a lot of lead shielding. Which would stop the blue glow. Damn. Besides - do dwarves get cancer?
And if you want to get technical, you forget that water seeping out of stone is the perfect incubator for various pathogens, including ebola. But this is dwarf fortress, and that stuff doesn't happen. A bloody miner, can dig out a wall which leads to direct magma flow - With his copper pick, before outrunning the magma and leaving it blocked up with a chalk floodgate. Meanwhile the smith above it, can tap directly into the magma to heat his smithing materials? Face it - Realism and dwarf fortress don't match - Only dwarf fortress and awesome.