Nitrogen is not toxic. Nitrogen is one of the main components of air, usually colorless and odorless gas, generally accounting for 78% of the total air. Although nitrogen is non-toxic, but if the nitrogen content of the air is high, so that the partial pressure of inhaled oxygen drops, it will lead to hypoxia and asphyxiation. When inhaling too high a concentration of nitrogen gas caused by hypoxia, initially will feel chest tightness, shortness of breath, weakness, followed by symptoms of irritability, excitement and nerve confusion, serious patients can enter a coma state. With further hypoxia, the patient may rapidly enter a coma and die due to respiratory and cardiac arrest.