![]() The concentration of oxygen can reach as high as 80% and amplify flammability and explosion hazards. The concentration of oxygen in the condensed air will increase and lead to oxygen enriched conditions. In many situations LN2 and LHe2 can condense the surrounding air. Therefore, always consult with the most appropriate reference when selecting materials for cryogenic applications. Carbon steel, metals, plastics, porcelain, and many other materials increase their brittleness in contact with cryogen and become susceptible to failure or malfunction. This ice can cause components or systems to malfunction (e.g., can plug vent lines and impede valve operation) or can damage piping systems. The extremely low temperatures associated with cryogenic liquids can easily condense moisture from the air and cause ice formation. ![]() Oxygen deficiency monitors should be used in these areas. Large volumes of cryogen liquid used in small laboratory spaces or in poorly ventilated areas increase the asphyxiation hazard. Even well-ventilated lab spaces that have pits or other low-lying areas could have the oxygen displaced by this cold, dense gas. In the case of liquid argon and liquid nitrogen, the gas generated from malfunctioning equipment or spills will be cold and denser than ambient air. These ratios mean that any accidental release or overflow of these cryogenic liquids will quickly boil into gas and create an asphyxiation hazard by displacing the oxygen content of the surrounding area. LN 2 is approximately 696 to 1, (by volume).Cryogenic fluids have large liquid-to-gas expansion ratios: Therefore, it is important to evaluate the pressure relief valve, venting valve, rupture disk and integrity of the container at least every month or before using it. Cryogenic liquid storage at warm temperature for an extended time can cause flash vaporization and produce extremely high pressure. Contact with the cryogenic liquids causes not only frostbite or cryogenic burns but can also damage materials like water pipes, flooring, sinks, and electrical cables.Ĭryogens are stored in confined containers such as pressurized dewars and cylinders. Liquid cryogens have an extremely low temperature. The SOP should include the manufacturer’s instructions regarding the use of and controls for commercially obtained cryogen equipment. Include procedural information regarding the use of equipment. It is recommended to create a Standard Operating Procedure (SOP) to include a description of the work being performed and have this available for all lab workers. ![]() ![]() Oxygen-enriched atmospheres may lead to violent reactions, such as rapid combustion or explosions, with incompatible materials.īefore the beginning of any experiment or work related to cryogens, all personnel must be familiar with cryogens, equipment, and the system they will be using. The following table summarizes the physical properties of common cryogens: CryogenĪ Although oxygen does not burn, it will support combustion. Liquid helium, liquid hydrogen and liquid oxygen present additional hazards that liquid nitrogen and liquid argon do not. Liquid nitrogen is the most frequently used cryogen on campus. This definition does not include liquid propane, liquid butane, liquid acetylene, or liquefied natural gas (methane). This definition includes liquid nitrogen (LN2), liquid argon (LAr), liquid helium (LHe), liquid hydrogen (LH2), and liquid oxygen (LO2), among others. A cryogen or cryogenic liquid is defined by the National Institute for Standards and Technology (NIST) as any liquid with a boiling point below 93K (-180☌ or -240☏) at 1 atmosphere of pressure.
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