OK all you perverts, that's enough speculation. Nolin can indeed produce flame (real flame, Cntxt, not Continual Flame) from any part of his anatomy at will. He does not feel the heat of the flame, but he can certainly burn nouns (people, places or things, dontcha know) in the viscinity if he's not careful.
That said, the flames are at Nolin's command. He can quench or ignite them as he pleases. Their default setting is off. While it is theoretically possible for him to have a hunka, hunka actually burning love, I can't think why he'd want to. Third degree burn is not usually considered a turn on. His undies and the rest of his clothes are not fire proofed, although he does have a fire proof pillow. When he first became one with the phoenix, the flames came out only as his hair (on his head. Sheesh, you people), but he couldn't turn it off. Hence the need for the pillow.
The flames are used mostly for effect now. People get really creeped out when your eyebrows burst into flame, or just the tip of one finger. Also, when Nolin casts Fly he grows a pair of firey wings which are pretty cool.
There, are you all happy? Go back to speculating about Pkitty and ColPladoh, willya?