Question

Can humans live without nitrogen?

Answer 1

In the atmosphere, $21\%$ oxygen and $79\%$ nitrogen is present at a pressure of $0.75$bar, which is breathable to humans. Up to height of $2500$m, breathing is manageable. Aircraft passengers and personnel experience the same every day. Breathing pure oxygen for unlimited time is possible if the pressure is not high. Pressure about $0.4$ bar is okay for breathing pure oxygen. At $1$ bar, breathing pure oxygen for one hour is possible, but beyond one hour, lung damage can occur.

Complete answer:
A mixture of helium and oxygen is breathable and is used by deep sea divers. But the mixture should not be inflammable and explosive.
At the pressure of $5$bar, a mixture of $4\%$ oxygen and $96\%$ hydrogen can be used.
The partial pressure of oxygen is a significant parameter. It should not be less than $0.2$bar. In addition, it should not be more than $0.4$bar.
The content of toxic or harmful gases like carbon monoxide, carbon dioxide, fluorine and chlorine should be low, so that it won’t be harmful for breathing. Gaseous chemical compounds can be a part of mixture, provided they are inert to the human body and not toxic to it.
Nitrogen is an inert gas and is not toxic. But breathing pure nitrogen is deadly to humans, since it displaces oxygen in the lungs.
Hence, humans are unable to live without nitrogen as there are severe complications, dynamics and various parameters are essential to be cooperative for life without nitrogen.
Besides, plants die without nitrogen as protein synthesis happens due to nitrogen. Without nitrogen, enzymes won’t be synthesized. If plants die, humans may also die.

Note:
Nitrogen is essential to humans because it is a part of amino acids, which act as building blocks of proteins and nitrogen. Though nitrogen is present in abundance in the atmosphere, it can’t be taken directly by animals and plants. Nitrogen passes through some reactions, which lead to a nitrogen cycle for entering into animals. Humans and animals need nitrogen as all of their tissue is made up of protein.