Burns cryogenic

Thermal burns result from the radiant heat emitted by a hydrogen fire and absorbed by a person, which is directly proportional to many factors including exposure time, burning rate, heat of combustion, size of the burning surface, and atmospheric conditions (mainly wind and humidity). For instance, thermal radiation flux exposure level of 0.95 W/cm2 may cause skin burns in 30 s. Cryogenic burns may result from contact with cold fluids or cold vessel surfaces. Exposure to large liquefied hydrogen spills could result in hypothermia, if proper precautions are not taken [17]. 

Low temperature The atmospheric boiling points for N2, C02, He, and Ar are -196, -79, -269, and -186°C, respectively. The potential for cryogenic burns must be addressed in operating and maintenance procedures and in specifying personal protective equipment requirements. 

Care should be taken during variable temperature experiments. When using liquid nitrogen for variable temperature work, skin contact should be avoided as severe frostbite or cryogenic burns can result. Also, certain parts of the equipment may become hot during the experiment. 

Cryogenic burn Frostbite damage to tissues as the result of exposure to low temperatures. It may involve only the skin, extend to the tissue immediately beneath it, or lead to gangrene and loss of affected parts. 

Contains refrigerated gas may cause cryogenic burns or injury... 

Accidents In the event of skin or eye contact with liquid oxygen, seek medical attention for cryogenic burns. Do not enter areas of high oxygen gas concentration, which can saturate clothing and increase its flammability. Ventilate area to evaporate and disperse oxygen. 

Cryomicrotome with microtome blades (e.g., Shandon Cryostat, Thermo Fisher Scientific), frozen specimen embedding medium (FSEM, Shandon Cryomatrix, Thermo Fisher Scientific, Inc., Waltham, MA, USA), and liquid N2. CAUTION It causes suffocation when present at amounts sufficient to reduce oxygen concentration below 19.5%. Contact with tissue can cause severe cryogenic burns. Always handle with protective gloves. 

Liquid hydrogen and the cold gas evolving from the liquid can produce severe cryogenic burns similar to thermal burns upon contact with the skin and other tissues. The eyes can be injured by exposure to the cold gas or splashed liquid that would otherwise be too brief to affect the skin of the hands or face. Contact between unprotected parts of the body with uninsulated piping or vessels containing liquid hydrogen can cause the flesh to stick and tear when an attempt is made to withdraw. 

In the Chemical Index, there are also frostbite notations for liquid gases with risk for cryogenic burns, for example, from Methane or Methyl vinyl ether. The chemicals are noted as frostbite hazards in the NIOSH Pocket Guide to Chemical Hazards (DHHS-NIOSH Publication No 2004-149, September 2005). 

Because the magnet is essentially a Dewar containing liquid nitrogen and liquid helium, the biggest risk is from those cryogens. The first risk is from the low temperatures of these liquids (liquid helium boils at about -270°C) which can cause serious burns. The second risk is of asphyxiation as the cryogens boil off. 

Liquid anhydrous ammonia in contact with the eyes may cause serious injury to the cornea and deeper structures and sometimes blindness on the skin it causes first- and second-degree burns that are often severe and, if extensive, may be fatal. Vapor concentrations of 10,000 ppm are mildly irritating to the moist skin, whereas 3 0,000 ppm or greater causes a stinging sensation and may produce skin burns and vesiculation. With skin and mucous membrane contact, burns are of three types cryogenic (from the liquid ammonia), thermal (from the exothermic dissociation of ammonium hydroxide), and chemical (alkaline). ... 

It is well known that exposure of the human body to cryogenic fluids or to surfaces cooled by cryogenic fluids can result in severe cold burns since damage to the skin or tissue is similar to that caused by an ordinary burn. The severity of the burn depends on the contact area and the contact time prolonged contact results in deeper burns. Severe burns are seldom sustained if rapid withdrawal is possible. 

Almost any flammable mixture will, under favorable conditions of confinement, support an explosive flame propagation or even a detonation. When a fuel-oxidant mixture of a composition favorable for high-speed combustion is weakened by dilution with an oxidant, fuel, or an inert substance, it will first lose its capacity to detonate. Further dilution will then cause it to lose its capacity to burn explosively. Eventually, the lower or upper flammability limits will be reached and the mixture will not maintain its combustion temperature and will automatically extinguish itself. These principles apply to the combustible cryogens hydrogen and methane. The flammability and detonability... 

The growing technology provided experience in coping with the more conventional cryogenic hazards associated with material s brittleness, with cold flesh "burns," and with liquid to gas expansion in confined spaces. 

Within the last one and a half decades, it became possible to perform experiments directly on the atomic and molecular level. This came with the improvement of existing experimental techniques such as electron microscopy, where the resolution was increased to make single atoms visible [1] high-resolution spectroscopy of single ions or atoms trapped in a radio frequency field or in focused laser beams [2-4] and the spectroscopic isolation of single molecules in solids at cryogenic temperatures [5-7], which evolved from spectral hole-burning spectroscopy. 

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