Monoplace Delivery System

Monthly Hyperbaric Safety Notice: May 2008

LOX Farm - Spring Cleaning!

Background

The liquid oxygen (LOX) farm housed at medical campuses is essential for the operation of the hyperbaric chamber. NFPA 55 Standards for the Storage, Use and Handling of Compressed Gases and Cryogenic Fluids in Portable and Stationary Containers, Cylinders, and Tanks cites in the 2005 chapter 8, table 8.6.2, the minimum separation between these stationary cryogenic containers and exposures hazards. Regular inspection of the LOX farm is necessary to ensure this standard is maintained.

The Issue

Oxygen is the second largest component of the atmosphere, comprising 20.8% by volume. Liquid oxygen is pale blue and extremely cold. Although nonflammable, oxygen is a strong oxidizer. Oxygen will react with nearly all organic materials and metals usually forming an oxide. Materials that burn in air will burn more vigorously in oxygen. Equipment used in oxygen service must meet stringent cleaning requirements and systems must be constructed of materials that have high ignition temperatures and that are non-reactive with oxygen under its service conditions. Storage vessels should be manufactured to American Society of Mechanical Engineers (ASME) codes and designed to withstand the process temperatures and pressures. Liquid oxygen is a cryogenic liquid. Cryogenic liquids are liquefied gases that have a normal boiling point below -238°F (-150°C). Liquid oxygen has a boiling point of -297.3°F (-183.0°C). Because the temperature difference between the product and the surrounding environment is substantial—even in the winter—keeping liquid oxygen insulated from its surroundings is essential. Extensive tissue damage and cryogenic burns can result from exposure to liquid oxygen or cold oxygen vapors. This product also requires special equipment for handling and storage. Oxygen is often stored as a liquid, although it is used primarily as a gas. Liquid storage is less bulky and less costly than the equivalent capacity of high-pressure gaseous storage. A typical storage system consists of a cryogenic storage tank, one or more vaporizers, a pressure control system, and all piping necessary for filling, vaporization, and supply functions. Vaporizers convert the liquid oxygen into a gaseous state. A pressure control manifold then controls the gas pressure that is fed to the application. Piping design should follow similar codes, as issued by the American National Standards Institute (ANSI).

Materials easily ignited in air not only become more susceptible to ignition, but also burn with added violence in the presence of oxygen. These materials include clothing and hair, which have air spaces that readily trap the oxygen. Any clothing that has been splashed or soaked with liquid oxygen or exposed to high oxygen concentrations should be removed immediately and aired for at least one hour. Personnel should stay in a well-ventilated area and avoid any source of ignition until their clothing is completely free of any excess oxygen. Clothing saturated with oxygen is readily ignitable and will burn vigorously. Do not permit smoking or open flames in any areas where liquid oxygen is stored or handled. Do not permit liquid oxygen or oxygen-enriched air to come in contact with organic materials or flammable or combustible substances of any kind. Some of the organic materials that can react violently with oxygen when ignited by a spark or even a mechanical shock are oil, grease, asphalt, kerosene, cloth, tar, and dirt that may contain oil or grease.

Bottom Line

As spring time approaches, so does the emergence of new leaves, weeds and grasses. These combustible items, to include paper or other debris must have a minimum distanceof 15 feet away from any bulk liquid cryogenic gas. If items such as these are observed in the vicinity, speak with local facilities management to have them removed in order to ensure this standard is met.

Stacy Handley, RN, BSN, ACHRN, CWCN, CHT

Stacy Handley Stacy is Vice President of National Baromedical Services. She assumed her present position following several years as nurse manager of the NBS hyperbaric medicine service at Memorial Hospital, in Colorado Springs, Colorado. Stacy oversees the patient care aspects of the NBS network, conducts quality assurance and compliance assessments and preceptors all new NBS nurse managers. Additional responsibilities include marketing and promotion of NBS service lines and generation of monthly safety notices. Stacy is Member at Large for the Undersea and Hyperbaric Medical Society Associates and a board member for the Baromedical Nurses Association. She has trained as a Hyperbaric Safety Director and a UHMS faculty accreditation surveyor, and is a graduate of the Medical University of South Carolina ‘Wound Care Specialty Course’ through which she obtained her wound care certification

Full Panel of Safety and Technical Correspondents

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