Some Characteristics Of Cryogenic Gases

By Grace Rivas

Cryogenic gases or cryogens refer to gases that have been maintained at a temperature of less than 123K or -150 degrees Celsius. At this temperature they usually turn to liquid. There are three main types of cryogens that include flammable liquids, oxygen and inert gases. Inert liquids are those that are usually unreactive. Examples include neon, nitrogen, krypton, argon and helium. Highly flammable types are the types that burn easily in air.

There are many uses for the cryogens. In the medical field, they are commonly in cryosurgery. Here, they help in treatment of cancer by destroying some of the malignant cells. They are also used in the preservation of both animal and human tissues for future use. Some reactions are associated with production of heat and the cryogens help in the maintenance of a lower temperature.

There are a number of health hazards associated with the use and storage of the cryogens. One of them is that the cryogenist or any other person that handles these products is exposed to very cold temperatures that may cause tissue injury. The resultant damage is similar to that caused by a thermal burn. Delicate mucosal membranes such as the conjunctiva are the most vulnerable. Affected parts of the skin characteristically appear waxy yellow.

The other major risk is asphyxiation. This is caused by displacement of ordinary air from the ground as the cooling cryogens expand. Consequently, the amount of oxygen in the ordinary air is reduced and respiration is compromised. The destruction of the lungs by the cryogens makes the situation worse. The risk for asphyxiation is particularly high in enclosed spaces.

Rapid expansion of the highly flammable gases may cause an explosion. Methane, hydrogen and carbon monoxide are some of the examples. Hydrogen mixes with air at different concentration forming an easily ignitable mixture. Liquid oxygen on the other hand can cause the combustion of materials considered non-combustible such as stainless steel, cast iron and carbon. When materials are soaked in the liquid they remain flammable for hours.

Due to the many associated risks, one needs to take precautions. Proper thermal insulation prevents ignition. The insulation should be done to the containers and the pipes that are used in the delivery of the cryogens. Special flasks that are non-pressurised are available in the market. They have a loosely fitting cap that allows for the escape of excess pressure but keeps moisture out of the vessel.

It is important that put on personal protective clothing at all times. The clothes must also be maintained clean and dry at all times. They should be well-fitting and cover arms and legs. If the material penetrates your gloves, remove them as soon as possible. For protection of the eyes and the face, googles or a facial shield should be used.

Cryogenic gases are very important and have a wide range of applications both domestically and in an industrial setting. It is important that one learns how to properly handle them to prevent serious accidents. The general advice is that one should always read the instructions and they should consult if unsure about anything.

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