little oxygen. This means that blood passing the lungs on the way to the brain has no oxygen to transport. When blood carrying very low oxygen reaches the brain, consciousness is rapidly lost, within one or two breaths. It is the lack of oxygen in the inhaled gas that causes death, not the particular gas itself.
For the process to work, it is important that the air in the lungs (with 21% oxygen) is quickly and fully replaced with the inert gas. For hypoxia to occur, the person empties their lungs of air (big breath out). They then replace this with a deep, full inhalation of the gas (nitrogen or argon) which contains 0% oxygen. With good lung function (and practice) this can be achieved with a single exhale/ inhale cycle. A problem associated with using this method, however, is that lung disease (or poor technique) can prevent a full exchange of gas. If a person has lung disease and is concerned about the use of this method, it is advised that they undergo a test to measure their lung function (spirometry). A lung function test gives an indication of whether this strategy is appropriate for them. (See the section on spirometry screening, later in his Chapter.)
It is important to note that the inert gas, itself, does not interact with the body. Nitrogen, Argon or Helium all have no taste or smell. All quickly dissipate after death. While Helium and Argon can be detected at autopsy, there is no test that can reveal the use of a Nitrogen-filled Exit bag. This makes Nitrogen particularly useful for those who don’t wish their cause of death to be established. (Of course, this presupposes that the equipment will be removed before the body is ‘discovered’. In some jurisdictions this can be an offence so check your local laws if you think this is a strategy of interest).