The main elements which compose the terrestrial atmosphere, in terms of volume, and their proportion:
|Dinitrogen (N2)||780,840 ppmv||78.084 %|
|Dioxygen (O2)||209,460 ppmv||20.946 %|
|Argon (Ar)||9,340 ppmv||0.9340 %|
|Carbon dioxide |
|400 ppmv||0.0400 %|
|Neon (Ne)||18.18 ppmv||0.0009%|
|Helium (He)||5.24 ppmv||0.0003%|
|Methane (CH4)||1.745 ppmv||0.0001%|
|Krypton (Kr)||1.14 ppmv||-|
|Dihydrogen (H2)||0.55 ppmv||-|
|Nitrogen monoxide (NO)||0.5 ppmv||-|
|Xenon (Xe)||0.09 ppmv||-|
|Ozone (O3)||0.07 ppmv||-|
|Nitrogen dioxide (NO2)||0.02 ppmv||-|
|Iodine (I2)||0.01 ppmv||-|
Dioxygen is the other name for oxygen. It is the gaseous state of oxygen, oxygen alone is composed of a single molecule O.
It is used in the combustion, the steel industry, the petrochemistry, the bleaching of the paper, the reprocessing of chemical waste, in normobaric and hyperbaric oxygen therapy.
So we think that we breathes mainly oxygen, but in fact no, it is in the vast majority diazote.
Nitrogen is used as a cryogenic gas, to conserve food, it is used in scuba diving to adjust the composition of the mixture, in pesticides to kill insects by asphyxiation, to inflate tires.
If we were to entering into a room filled with only dinitrogen, anoxia (oxygen depletion in human tissues) would be risked, but no suffocation sensation.
Nitrogen is safe for the planet, as long as oxygen is present in sufficient quantities.