page_title: Liquefied petroleum gas
section_title: Fire/explosion risk and mitigation
hierarchical_section_title: Liquefied petroleum gas / Fire/explosion risk and mitigation
caption_attribution_description: English: Natural gas. in Esslingen am Neckar, Germany Deutsch: Ein Erdgas-Kugelspeicher in Esslingen am Neckar
context_page_description: Liquefied petroleum gas or liquid petroleum gas, is a flammable mixture of hydrocarbon gases used as fuel in heating appliances, cooking equipment, and vehicles.
  It is increasingly used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons in an effort to reduce damage to the ozone layer. When specifically used as a vehicle fuel it is often referred to as autogas.
  Varieties of LPG bought and sold include mixes that are mostly propane, mostly butane, and, most commonly, mixes including both propane and butane. In the northern hemisphere winter, the mixes contain more propane, while in summer, they contain more butane. In the United States, mainly two grades of LPG are sold: commercial propane and HD-5. These specifications are published by the Gas Processors Association and the American Society of Testing and Materials. Propane/butane blends are also listed in these specifications.
  Propylene, butylenes and various other hydrocarbons are usually also present in small concentrations such as C2H6, CH4 and C3H8 Butane. HD-5 limits the amount of propylene that can be placed in LPG to 5% and is utilized as an autogas specification.
context_section_description: In a refinery or gas plant, LPG must be stored in pressure vessels. These containers are either cylindrical and horizontal or spherical. Typically, these vessels are designed and manufactured according to some code. In the United States, this code is governed by the American Society of Mechanical Engineers (ASME).
  LPG containers have pressure relief valves, such that when subjected to exterior heating sources, they will vent LPGs to the atmosphere or a flare stack.
  If a tank is subjected to a fire of sufficient duration and intensity, it can undergo a boiling liquid expanding vapor explosion (BLEVE). This is typically a concern for large refineries and petrochemical plants that maintain very large containers. In general, tanks are designed so that the product will vent faster than pressure can build to dangerous levels.
  One remedy that is utilized in industrial settings is to equip such containers with a measure to provide a fire-resistance rating. Large, spherical LPG containers may have up to a 15 cm steel wall thickness. They are equipped with an approved pressure relief valve. A large fire in the vicinity of the vessel will increase its temperature and pressure. The relief valve on the top is designed to vent off excess pressure in order to prevent the rupture of the container itself. Given a fire of sufficient duration and intensity, the pressure being generated by the boiling and expanding gas can exceed the ability of the valve to vent the excess. If that occurs, an overexposed container may rupture violently, launching pieces at high velocity, while the released products can ignite as well, potentially causing catastrophic damage to anything nearby, including other containers.
  People can be exposed to LPG in the workplace by breathing it in, skin contact, and eye contact. The Occupational Safety and Health Administration (OSHA) has set the legal limit (Permissible exposure limit) for LPG exposure in the workplace as 1000 ppm (1800 mg/m³) over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 1000 ppm (1800 mg/m³) over an 8-hour workday. At levels of 2000 ppm, 10% of the lower explosive limit, LPG is considered immediately dangerous to life and health (due solely to safety considerations pertaining to risk of explosion).
caption: A spherical gas container typically found in refineries
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