Nitrous doesn't burn, it requires fuel. In the case of the fires, it is the fuel that is on fire. For some reason the fuel system has been compromised. What is perceived as a nitous backfire is usually caused by an initial misfire caused by a too rich condition, if fuel has puddled in the intake and the nitrous is flowing, the misfire ignites the two and a subsequent second event.
It has to be strange or rare for the nitrous to remain on after the misfire. There have been two fires shown recently in posts. Those are the first two that I have seen in my five years on this board. The one from five years ago (garage fire) doesn't count, nitrous wasn't the root of that problem. Getting back to the recent events, my guess is that they were direct port installations and probably had massive mechanical failures. When you are utilizing the intake tubes (on street side of throttle bodies) like we typically do you are far safer and many reasons, the penalty is that power output may not be as great.
