The graph below of lung-oxygen concentration as a function of time for normal breathing, holding your breath, and for being in an oxygen-free atmosphere clearly illustrates how dangerous this last scenario truly is.
chapelboro.com
How nitrogen kills
Nitrogen is an inert gas — meaning it doesn't chemically react with other gases — and it isn't toxic. But breathing pure nitrogen is deadly. That's because the gas displaces oxygen in the lungs. Unconsciousness can occur within one or two breaths, according to the
U.S. Chemical Safety and Hazard Investigation Board.
Nitrogen inhalation doesn't cause the same panicked feeling that suffocation does, because the person continues to exhale
carbon dioxide. Rising carbon dioxide in the blood is what triggers the
respiratory system to breath. These levels are also responsible for the burning and pain that happens when you hold your breath for too long. Because the carbon dioxide levels in the blood never rise with nitrogen inhalation, these symptoms don't occur.
Hypoxia, or a lack of oxygen, kills pretty quickly. According to the U.S. National Library of Medicine, brain cells start dying
within 5 minutes of oxygen deprivation starting. Death follows rapidly.
After an ongoing shortage of execution drugs that has left states scrambling, Oklahoma authorities have announced that it will use nitrogen gas to execute death-row inmates.
www.livescience.com
In the report favoring nitrogen as an execution method supplied to Oklahoma state legislators in 2015, the authors cited a 1961 study. That research found that human volunteers who hyperventilated, or rapidly breathed, pure nitrogen fell unconscious within 20 seconds.
