As discussed earlier, for a peaceful and quick hypoxic death, it is essential that there be no oxygen (or air) in the gas being breathed. It is the sudden reduction in oxygen level (from the 21% in air) to effectively 0% within the confines of the Exit bag, that results in the immediate loss of consciousness (LOC) and subsequent death. If the supplied gas (Nitrogen, Argon or Helium) has any oxygen present, the method may fail.
Note: Since the common uses of compressed Nitrogen (eg. brewing, food preservation) depend on an absence of oxygen, the issue of gas contamination does not arise.
Testing Gas Purity
1. Obtain an accurate oxygen sensor eg the Detector CY-12C Oxygen Analyzer, cost ~US$100 - click HERE (see Fig)
2. Calibrate the sensor by setting the gauge to 21% in air 3. Attach the flow regulator jet to the gas cylinder and con- nect the hose to run a steady flow (eg 1 lire/ min) of gas into the filtered input of the gauge. (See Fig).
4. Let the gas flow until a steady reading is obtained on the most sensitive gauge setting.
The [O2} reading should be < 2% if the gas is to be used.
At the end of the test, check the cylinder pressure to ensure that there is still an adequate supply left for a hypoxic death.