Oxygen is one of the main components in the air, accounting for 21.0% of the normal air, making it a component in all animals and plants. However, the concentration of oxygen is too high or too low will be harmful to people. Excessive partial pressure of oxygen will cause "oxygen poisoning".
Under normal pressure, when the concentration of oxygen exceeds 40%, the possibility of oxygen poisoning will occur. There are two main types of oxygen poisoning in human beings: (1) the lung mainly occurs in the oxygen partial pressure of 1-2 atmospheres, which is equivalent to about 40% - 60% of the inhaled oxygen concentration. At the beginning, there was a little discomfort behind the sternum, accompanied by a light cough, and then felt chest tightness, burning feeling behind the sternum, dyspnea and cough aggravation. Severe pulmonary edema and asphyxia may occur. (2) Neurotype - mainly occurs when the partial pressure of oxygen is more than 3 atmospheres, equivalent to the concentration of inhaled oxygen more than 80%. At first, there were more muscle twitches in the mouth or face, pale face, dizziness, heart rate acceleration and collapse, and then there were convulsions, coma, respiratory failure and death.
The treatment of oxygen poisoning should be timely, strengthen ventilation, change air intake, rest quietly, keep respiratory tract open, and give sedative and anticonvulsant drugs to prevent secondary infection of lung. The key to the treatment of anoxia lies in removing the cause of anoxia and preventing brain edema.
Generally, evacuate the site immediately, inhale oxygen, use positive pressure to supply oxygen, and use high pressure oxygen treatment when conditions permit. When the heartbeat stops, it is necessary to carry out artificial respiration and heart massage to resuscitate the patient as soon as possible.
Liquid oxygen can stimulate skin and tissue, causing cold burns. When the skin is exposed to liquid oxygen, it should be washed with water immediately, and those who are seriously injured should be treated with medical treatment. Oxygen evaporated from liquid oxygen is easy to be absorbed by clothes, and any kind of fire source can cause sharp combustion.
If the supply of oxygen is insufficient or the metabolic process of oxygen in the body is blocked, enough oxygen can not be obtained or used normally, resulting in a series of changes, even life-threatening, which is called "anoxia". Here are the symptoms and consequences of different hypoxia conditions:
Liquid oxygen is stored and transported in Dewar or tank car. It must be isolated from combustibles during storage to avoid heating. The liquid oxygen tank car is best placed outdoors. Oxygen is non corrosive, however, aluminum alloys should be avoided as far as possible. When there is moisture, it will corrode the metal, so the moisture should be removed in advance for the device. Applicable materials are stainless steel, copper, copper alloy, nickel, nickel alloy, glass and other materials. Carbon steel and low alloy steel should be avoided. For liquid oxygen department, polytetrafluoroethylene, polytetrafluoroethylene polymer and fluororubber shall be used, and combustible materials such as polyethylene and polypropylene shall be avoided. In case of fire, when it is too late to transfer, the tank car shall be watered and cooled to prevent the fire from being heated and exploded and the liquid oxygen flowing out after the explosion. But when watering, be sure to avoid direct water on the safety valve to prevent it from cooling and failure.
When the leaked liquid oxygen causes the burning of wood, paper, etc., if possible, first cut off the air flow, stop the leakage, and then use sufficient water to extinguish it. When liquid oxygen and liquid fuel meet and start a fire, the following methods shall be used for fire fighting. When the leaked liquid oxygen flows to a large amount of fuel to start a fire, first cut off the liquid fuel source, and then put out the fire. When liquid fuel and liquid oxygen have been mixed and have not started a fire, all fire sources shall be cut off immediately, and the liquid oxygen shall be allowed to evaporate by itself. If it is water-soluble fuel, it can be diluted with water to suppress the fire. However, this method is not suitable for non water soluble fuel. It is necessary to wait until all liquid oxygen evaporates before using appropriate extinguishing agent to extinguish the fire.