Chlorine gas is a toxic gas. When inhaled by the human body through the respiratory tract, chlorine dissolves in the respiratory mucosa and reacts chemically with the water in the mucosa to produce hypochlorous acid and hydrochloric acid, thus damaging the respiratory mucosa. Generally speaking, it takes more chlorine gas inhalation in a short period of time, or continuous chlorine gas inhalation for a long period of time to produce toxicity. 1. mild poisoning: the patient will experience symptoms of upper respiratory tract irritation such as burning sensation, tingling, choking, runny nose, sneezing and coughing, as well as chest tightness, chest pain, slight dizziness and headache. 2. moderate poisoning: the patient will have episodes of dry cough, in addition to increased symptoms of mild poisoning. There is a small amount of hemoptysis, and at the same time, there will be persistent pain behind the sternum, dyspnea, accelerated pulse, heartbeat and respiration, sometimes the skin and mucous membranes will appear blue, and accompanied by headache, dizziness, irritability, nausea, vomiting and abdominal pain; 3. Severe poisoning: if a large amount of high concentration of chlorine gas is inhaled, there will be an immediate and persistent severe cough or coughing of blood, a feeling of tightness in the chest causing difficulty in breathing, severe headache, and usually Pulmonary edema will occur in 1-2 hours, and the patient will cough up a lot of pink foam-like sputum, have difficulty breathing, and both lungs will be covered with wet rales. In severe cases, the patient will immediately fall into coma, blood pressure drops, pulse rate increases, spasmodic edema occurs in the larynx and bronchi and even suffocation, and can cause reflex respiratory depression and cardiac arrest, leading to lightning-like death and burning acute dermatitis on exposed areas of the skin. There are three common causes of chlorine poisoning, the first is when equipment is damaged or personal protection is inadequate during industrial use; the second is when the container holding the chlorine is damaged during transportation, when the cylinder mouth seal fails or when protection is neglected; the last is when chlorine-containing bleach is mistakenly mixed with acid during disinfection in homes, swimming pools or other places, which can react rapidly to produce large amounts of chlorine gas in poorly ventilated This can lead to serious poisoning and even death in poorly ventilated rooms. Therefore, it is important to pay attention to the safety of use in daily work production and household disinfection.