I apologize for trampling on the wrong forum but I'm a noob, anyhoo.
My idea has been used sort of but it's not on the market in this form so I'm a bit hesitant to discuss in great detail just yet but.... As for the 'inert' part I imagine that CO2 would cause an uproar being a 'greenhouse' gas and all, Nitrous is an Oxidizer so that would be out, same goes for compressed air and straight oxygen. Helium is controlled and more expensive so I think that leaves good ole compressed Nitrogen. Inert, yes, cheap, yep. Asphyxiant, oh yeah but--I will be running a motorcycle so ample ventilation is of no concern.