A friend of mine, Alexzander the Baked, had an idea that while in theory seemed great but once in reality was flawed. His idea was to have a built in bong system installed into your ventilation system that would smoke up the entire house and you would get stoned off your ass. The problem is that once the house is smoked out, the air will be running a bit thin. You will be to high to notice that you a running out of oxygen and would die of asphyxiation. What a way to go, dying in a cloud of ganja smoke.
Below is my interpretation on what that might look like. Gotta love MS Paint.