>>4702914With each breath you are taking in 78% Nitrogen and only about 20% Oxygen. Our bodies do not use the Nitrogen in the gas state during respiration so it goes in and out without doing anything.
The composition of air remains the same even up to 40,000m above sea level, then Nitrogen gas starts taking up a higher portion and percentage at higher altitudes.
In spacecraft Oxygen only environments are highly flammable and this was discovered when Soviet Cosmonaut Valentin Bondarenko received fatal burns from a fire in an Oxygen rich capsule. Liquid Oxygen (like liquid Hydrogen) is also extremely flammable and is used as rocket fuel in some rockets. This is why manned space travel for long periods of time is so difficult and dangerous, as you need to supplement Oxygen with another inert gas to avoid the possibility of the capsule catching fire, so you must cart around Nitrogen containers in the capsule as well.
If the Earth's atmosphere lacked Nitrogen gas as a large portion of its atmosphere then life as we know it would not be able to survive on Earth's surface and might only be confined to underground, while other organisms adapt to the reduced pressure. Nitrogen and the Nitrogen gas cycle is a critical element needed for life on Earth, as is Oxygen as a catalyst in biological organisms, including humans.
The human body uses Nitrogen in Amino acids in our DNA and in protein that we consume.
