The danger of air entering into blood vessels is mainly to cause air embolism. If the air entering the human body through the intravenous infusion tube is less than 2ml, it will be mostly absorbed by the body itself. If the air entering the human body through other ways reaches 5ml in the blood vessel, there will be a risk of air embolism, and the human heart and lungs will be in danger of life because of air embolism. The main symptoms of air embolism are causing patients to have dangerous vital signs such as irritability, fear, dyspnea, severe chest pain, back pain, decreased blood pressure, dilated pupils, and irregular heart rate, and finally, the patient may die clinically due to lack of oxygen. Air enters the blood vessels and must be treated symptomatically under intensive care such as ICU in the hospital to prevent the danger.