78 percent of the air we breathe in is nitrogen gas. However, breathing in air with such a high percentage of nitrogen is not harmful or toxic to our body, as nitrogen is an inert gas, which means it is unreactive or it does not chemically react with other gases to produce any toxic gaseous compound. Being unreactive, nitrogen does not react with haemoglobin either and therefore it does not participate in respiration at all. All of the nitrogen which is inhaled, is given out during exhalation.