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Refrigerator bomb: Organic reagents are used in extraction or dialysis; they are placed in an open refrigerator, and when the organic gases reach a critical concentration, they are ignited by the electric sparks generated when the refrigerator compressor starts up. On October 6, 1986, a refrigerator at a research institute affiliated with the Chinese Academy of Sciences exploded ； On December 15, 1987, a refrigerator in a laboratory at the Ningxia Academy of Agricultural Sciences exploded ； On July 20, 1988, a “Shasong” brand refrigerator in the home of a teacher at Nanjing Normal University exploded. In just a few years, there have been over 10 reported cases of refrigerator explosions. The cause of these accidents was not the quality of the refrigerators themselves, but rather the fact that people placed chemical substances such as petroleum ether, propane, benzene, and butane gas inside them. We know that the temperature inside a refrigerator is low; if chemicals with a low boiling point that are flammable and explosive are placed there, they will emit combustible gases under these low-temperature conditions. Even if the bottle cap is tightened tightly, low temperatures often cause the bottle body to shrink, the air valve to loosen, or even the bottle body to crack. The volatile combustible gases that are released mix with air to form explosive mixtures within the refrigerator; these mixtures can explode very easily when exposed to electrical sparks generated by the on/off operation of the temperature control switch (or other control switches). Therefore, refrigerator users must never casually store chemical substances in the fridge. Pouring oil into an open flame or using pliers to open a burning alcohol lamp while pouring alcohol into it with the other hand may cause the entire bottle of alcohol to catch fire and explode. In a liquid nitrogen bomb, samples are placed in glass or Eppendorf centrifuge tubes with caps, and these tubes are put into a container filled with liquid nitrogen. When taken out, the properties of the tube walls change, preventing them from withstanding the pressure of the expanding gas; or uneven pressure distribution occurs as a result of rapid heating, leading to an explosion. Therefore, people who wear glasses have an advantage—“Long live glasses!” ”Those who frequently work with liquid nitrogen should wear plastic goggles. (1) Hazard overview – Health hazards: This product is non-flammable but poses asphyxiation risks; skin contact with liquid nitrogen can cause frostbite. If an excessive amount of nitrogen is generated by vaporization at room temperature, it can reduce the partial pressure of oxygen in the air, leading to hypoxic asphyxia. (2) First aid measures for skin contact: If frostbite occurs, seek medical treatment. Inhalation: Quickly move to a place with fresh air and ensure smooth breathing. In case of difficulty breathing, administer oxygen. If breathing stops, perform artificial respiration immediately and seek medical attention. (3) Fire safety risk: If exposed to heat, the pressure inside the container increases, posing a risk of cracking and explosion. Fire extinguishing method: This product is non-flammable; use misted water to keep the containers in the fire area cool. Mist water can be used to spray and accelerate the evaporation of liquid nitrogen; a water gun should not be used to direct liquid nitrogen. (4) Emergency response to leaks: Quickly evacuate people from the contaminated area to an upwind location, and establish a barrier to restrict access. Emergency responders wear self-contained positive-pressure breathing apparatus and cold-weather gear. Do not come into direct contact with the spill. Cut off the source of leakage as much as possible. Prevent gases from accumulating in low-lying areas and exploding when exposed to a heat source. Use an exhaust fan to send the leaking gas to an open area. Leaking containers must be properly handled, repaired, and inspected before reuse. (5) Operational handling and storage precautions: Conduct operations in a closed environment and ensure good natural ventilation. Operators must be trained and strictly follow the operating procedures. It is recommended that operators wear cold-resistant gloves. Prevent gas from leaking into the workplace air. Handle with care during transportation to prevent damage to the cylinders and accessories. Equipped with leak emergency equipment. Storage precautions: Store in a cool, well-ventilated area where the temperature should not exceed 50°C. (6) Personal protective equipment for the respiratory system: No special protection is generally required. However, when the oxygen concentration in the workplace air is below 19%, it is necessary to wear an air respirator, an oxygen respirator, or a long-tube mask. Eye protection: Wear a safety shield. Hand protection: Wear insulated gloves. Other protections: Avoid inhaling high concentrations and prevent frostbite. Toilet planes pour large amounts of organic liquids into the sewer system at once, causing flammable vapors to fill the sewers and posing a threat to those who smoke while using the toilet. Power supply leakage: Electric shock can occur when touching electrical switches, plugs/sockets, wires/patch panels, or the power connectors of electrophoresis devices with wet hands. Improper use of water near power sources and electrical appliances: In areas where water or reagents have flowed or splashed, there may be exposed 220V AC power cables, plugs, or leaking electrical equipment. First, unplug the electrophoresis tank, then turn off the electrophoresis apparatus (DC). When an electrical fire occurs, blindly using water to extinguish it is not advisable; instead, a 1211 dry chemical fire extinguisher, wet cloth/asbestos cloth, or fine sand should be used. Clothes over skin: Burning caused by the invisible washing solution, which occurs when one handles glassware taken out of the acid tank without any protection, or when one deliberately removes stockings, etc., in order to protect their clothes. Other common incorrect practices include pouring water into concentrated sulfuric acid, heating a reagent tube with the opening facing a person or looking down at the opening, and directly sniffing the gases escaping from the test tube. Add water to sulfuric acid – pour water into concentrated sulfuric acid ； When heating the reagent, point the tube opening toward yourself or look down at it. Supplement: Failing to monitor the temperature during heating or not adding zeolite can cause the container to boil over violently, resulting in injuries to others. A liquid nitrogen tank is not an oil bottle; do not support it after it spills. Liquid oxygen, liquid nitrogen, and liquid argon are all cryogenic liquefied gases. At 1 atmosphere of pressure (101.325 KPa), the boiling point of liquid nitrogen is -195.65°C℃ ； The boiling point of liquid argon is -185.71℃ ； The boiling point of liquid oxygen is -182.83°C. Contact with human skin and eyes can cause frostbite (cold burn). When cryogenic liquids vaporize into gases, their volume expands rapidly at 0°C and 101.325 kPa. 1L of liquid vaporizes into gas: oxygen is 800L ； Argon is 780L ； Nitrogen is 647L. In a closed container, the pressure rises due to the liquefied gas, which can easily lead to the risk of overpressure in the container. Radioactive isotopes – invisible killers. Improper handling of radioactive isotopes, such as not wearing gloves, failing to protect the head and chest, and discarding radioactive materials carelessly. Failing to report pollution when it occurs is a gamble on luck. The recovered materials contaminated with isotopes are not washed immediately after the experiment. Any attempt to evade or shirk responsibility will backfire and harm both others and oneself! To make it easier to wear slippers, wear them in any situation where there is a risk of slipping and getting injured: near acid tanks, in low-temperature laboratories, in wet areas with slippery surfaces, and when going up or down stairs. WHO Laboratory Biosafety Manual, 2nd Edition: Preventive Measures against Laboratory Transmissions 10. Do not wear sandals, slippers, or high-heeled shoes in the laboratory. Laboratory safety regulations of East China Normal University: 10. It is prohibited to work without a shirt, wearing tank tops, baggy pants, or slippers (except in areas with waxed floors indoors)… Safety regulations of Tianjin Institute of Materia Medica: 6. Wearing slippers is prohibited at work to prevent accidents. Risks associated with centrifuges: Improper operation of the equipment; centrifuge rotors that are not balanced, not axially symmetrical, or whose lids are not tightened properly; pressure cookers whose lids are not tightened diagonally, do not contain enough deionized water, or are not disinfected using an automatic process; placing paper, gauze, rubber, or plastic items in high-temperature ovens; forgetting to turn off the ultraviolet lights, resulting in prolonged exposure to ultraviolet radiation; when preparing triple-distilled water using a quartz distiller, turning on the power supply before turning on the cooling water… Combustion and explosion accidents and preventive measures: The three conditions necessary for a combustion or explosion to occur in a centrifuge are fuel, an oxidizer, and a source of ignition. The temperature of the material has a significant impact on combustion and explosion. 1. The cause of the accident is that a combustion explosion is more likely to occur when the temperature at which the material is processed in a scraper-type centrifuge is below its flash point, or when the temperature in a non-scrapper-type centrifuge is equal to or above its flash point. When the temperature of the material processed by a scraper centrifuge is equal to or higher than its flash point, the possibility of combustion and explosion is extremely high. 2. Protective measures involve the use of inert gases or other gases for protection ； To control the oxygen concentration, flow monitoring or pressure monitoring can be used; for positive-pressure operations, pressure monitoring is the preferred method. Generally, the oxygen concentration monitoring method can be used to strictly control the oxygen concentration. Mechanical injuries caused by centrifuges and preventive measures: Among the safety accidents related to centrifuges, most are caused by improper operation or violations of operating procedures. 1. The cause of the accident is that when material is fed into the centrifuge, it is not possible for the material inside the drum to be distributed absolutely evenly; in other words, an imbalance occurs. As a result, when the drum rotates at high speed, this imbalance leads to vibration of the drum. 2. As a preventive measure, an effective interlock cover protection device can be installed at the feed inlet of the safety enclosure to eliminate potential accident risks; that is, when the cover is in the open position, the interlock protection device must ensure that the machine cannot start ； Conversely, as long as the machine is running, the cover cannot be opened until the drum stops rotating safely. Drum rupture caused by corrosion and preventive measures: Corrosion is an issue that requires special attention when using centrifuges in fertilizer, chemical, and oil refining plants. Corrosion will thin the wall thickness and reduce the strength of components such as the centrifuge drum, leading to rupture accidents. 1. Cause of the accident: The drum operated for a long time in a corrosive medium, resulting in severe corrosion; as a result, the thinnest part of its drum wall became thinner than the minimum allowable wall thickness. The thickness of the casing (made of cast iron) is uneven, with variations ranging from 8 to 32 mm; this unevenness can cause the casing to break when the drum ruptures. 2. Preventive measures: The internal components of the drum and even the entire centrifuge should be made of corrosion-resistant materials wherever possible ； If it is not possible or not allowed to make such a selection for various reasons, then corrosion-resistant linings such as lead or plastic should be installed inside the centrifuge. Regularly check for corrosion in important components such as the centrifuge drum; if severe corrosion is detected, it should be repaired or replaced promptly ； The casing can be made of steel, with its manufacturing quality ensured. The dangers of high-voltage DC generators: During insulation testing, high-voltage DC generators are considered relatively dangerous instruments. Precautions: When using this instrument, the user must comply with Article 168 of the Electrical Safety Regulations, and install two clearly marked disconnection points before connecting the power supply to the tester. When replacing the test specimen and wiring, the two power supply disconnect points should be clearly separated first. Before the test, please check whether all the test wiring, control box, voltage multiplier tube, and the grounding wires of the test specimen are properly connected. The grounding wire of the test circuit shall be grounded at one point in accordance with the requirements of this instrument’s manual. For discharging large-capacitance test specimens, specialized discharge resistor rods are used to discharge the specimens. During discharge, the discharge rod should not be brought into contact with the test specimen immediately; instead, it should be gradually brought closer to the specimen. A certain distance of air gap is required for dielectric discharge to occur, during which a hissing sound is heard. Once no sound is heard, the discharge rod can be used to initiate discharge, and finally, the ground wire can be connected for discharge. At a direct current voltage of 200 KV or higher, even though the testers are wearing insulating shoes and are in an area at a safe distance, the spatial electric field distribution of high-voltage direct current causes different direct current potentials to develop on the bodies of several people standing nearby. Testers should not shake hands with each other or touch grounding electrodes with their hands, as this can cause mild electric shocks. This phenomenon is more noticeable in dry areas and during winter, but since the amount of energy involved is small, it generally does not cause any harm to the human body. The power supply for the control box of the high-frequency DC high-voltage generator is AC 220V±10%, 50Hz. If the power supply is provided by a 1/1 isolation transformer or by an on-site self-generated power source, it is necessary to manually connect one point of the power supply to ground.