The simplest way to achieve this is by filling a plastic bag with an inert gas and then to quickly place this bag over one’s head. To understand why the plastic Exit bag provides an easy and reliable way to die, a basic understanding of human physiology is helpful.
In normal everyday life, we live in an atmosphere that is 21% oxygen. Interestingly, when there is a decline in the level of oxygen in the air we are breathing, we do not experience alarm or concern. As long as one can breathe easily, the sensation one experiences as the oxygen level drops is that of disorientation, confusion, lack of coordination and eventual loss of consciousness.
This experience is sometimes likened to being drunk (alcohol intoxication). When the oxygen level becomes too low, death will result. Accidental hypoxic deaths are not uncommon and there is a number of scenarios that can bring them about. One example is the sudden drop in oxygen level that occurs when an aeroplane depressurizes at high altitude. This can lead to a rapid loss of consciousness and the death of all those on board.
When the plane de-pressurizes, passengers still breath easily. The problem is that there will be little oxygen in the inhaled air. This lack of oxygen will cause a sudden drop in the dissolved oxygen in the blood reaching the brain. This leads to loss of consciousness and death.
It is not uncommon for planes that have suddenly de-pressurized to travel on autopilot until they run out of fuel, well after everyone aboard has died. Witnesses (from planes sent to investigate) say that it often appears as though everyone on board has just gone to sleep.