LIQUID HELIUM

SECTION 2: Hazards identification

Main Hazards All Portable Cryogenic Containers (PCC’s) containing cryogenic liquids must be regarded as pressure vessels at all times. Excessive exposure to heat could cause the internal pressure to increase significantly with the consequent violent rupturing of the vessel. Users of liquid helium must also take special precautions in addition to those necessary for the safe handling of such inert liquefied gases as nitrogen and argon. The extremely low temperature of liquid helium makes these special precautions imperative. (1)It can solidify all other gases. (2) It causes air to condense on any uninsulated or inadequately insulated pipe through which it passes. (3) This can result in a localised oxygen-enriched atmosphere by the condensation of oxygen-enriched liquid air. Adverse health effects Liquid helium is non-life supporting. Chemical Hazards Atmospheric air will condense on exposed helium- cooled piping. Nitrogen, having a lower boiling point than oxygen, will evaporate first from condensed air, leaving an oxygen-enriched liquid. This liquid may drip or flow to nearby surfaces. To prevent the possible ignition of grease, oil, or other combustible materials which could come into contact with the air-condensing surfaces, such areas must be cleaned to “oxygen-clean” standards. Any combustible foam-type organic polymer insulation should be carefully applied to reduce the possibility of this air condensation. The oxygen-enrichment process - which if followed by an impact could set off an explosive burning of the foam. Helium is extremely inert and forms no known chemical compounds. Biological Hazards All precautions necessary for the safe handling of any gas liquefied at very low temperatures must be observed with liquid Helium. Extensive tissue damage similar to burns can result from exposure to liquid helium or cold helium vapours. Vapour Inhalation As Helium acts as a simple asphyxiant, death may result from errors in judgement, confusion, or loss of consciousness which prevents self-rescue. At low oxygen concentrations, unconsciousness and death may occur in seconds without warning. Eye Contact Cold vapour can cause severe burn-like injuries. Skin Contact Frostbite can occur from contact cold vapour. Ingestion N/A Carcinogenicity Severe cold burns could result in carcinoma.