Any method involving bleach, be it by gas or drinking, is going to be extremely painful and is more likely to seriously injure you rather then kill you. Also the gas method endangers everyone nearby and first responders. Probably not what you want to hear but it's the truth. The gas method, usually refered to as the "detergent method", can require special knowledge to make sure the chemicals are mixed properly. If not it can damage any soft tissue it touches. Just don't do it.