NOx mainly damages the respiratory tract. Inhalation of the gas initially causes only mild eye and upper respiratory tract irritation, such as pharyngeal discomfort and dry cough. Delayed pulmonary edema, adult respiratory distress syndrome, chest tightness, respiratory distress, coughing, foamy sputum, cyanosis, etc., often occur after a few hours to a dozen hours or longer incubation period. Pneumothorax and mediastinal emphysema may complicate. Late-onset obstructive bronchitis can occur about two weeks after the subsidence of pulmonary edema. Chronic effects are mainly characterized by neurological weakness syndrome and chronic inflammation of the respiratory tract. Pulmonary fibrosis occurs in individual cases. May cause dental erosion. After inadvertent inhalation, quickly remove from the scene to fresh air. Keep the respiratory tract open. If breathing is difficult, give oxygen. If breathing stops, artificial respiration immediately. Seek medical attention as soon as possible.