The Stovebolt Site Forums The Shop Area Engine Shop Running an engine without exhaust....Risky?

I have looked that subject up many times, and have really seen no hard evidence that that is anything other than a myth. I have no actual experience, other than driving to the muffler shop after I put the headers on. Mostly because it is simply too loud, and I don't need the possibility of being asphyxiated from the exhaust gas.