element in the universe after hydrogen and helium. At standard temperature and pressure, two oxygen atoms will bind covalently to form dioxygen, a colorless
Oxygen is a chemical element; it has the symbol O and its atomic number is 8. It is a member of the chalcogen group in the periodic table. It is highly reactive, a nonmetal, and a potent oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is the most abundant element in Earth's crust, making up almost half of the Earth's crust in the form of various
Unless non-flammable containers are used or all sources of ignition are eliminated, oxygen rich environments are extremely hazardous. Many materials including most metals burn faster in oxygen rich environments and ignite at lower temperatures. Concentrated O2 will allow combustion to proceed rapidly and energetically. Steel pipes and storage vessels used to store and transmit both gaseous and liquid oxygen will act as a fuel; and therefore the design and manufacture of O2 systems requires special training to ensure that ignition sources are minimized.
The 1967 fire that killed the Apollo 1 crew in a launch pad test spread so rapidly because the capsule was pressurized with pure O2 at slightly more than atmospheric pressure to force the doors against their seals. Once in space the exterior pressure would be minimal and the oxygen pressure would have been reduced to 5psi to reduce fire hazard. The ignition source for the fire was traced to an electrical surge under the seat of one of the astronauts, probably due to chafed wires.
Liquid oxygen spills, if allowed to soak into organic matter such as wood, petrochemicals, and asphalt, can cause these materials to detonate unpredictably on subsequent mechanical impact.
- The heat can be removed. The most common way to remove heat is to use water to absorb that heat, putting the fire out. However, some fires cannot be smothered, such as magnesium flames. They can burn in carbon dioxide, nitrogen, and some other elemental compounds. However, they cannot burn in noble gases such as helium. Reactions
Fires are usually combustion reactions that take carbon, hydrogen, and oxygen.[2] The products are commonly water and carbon dioxide, although there are other examples that avoid this generalization, such as burning magnesium in air, which makes magnesium oxide. Fires can occur in many ways. There are many types of fire.[3] There are wood fires, gas fires, metal fires, and more. Wood fires can usually be put out with water because water absorbs heat, but metal fires are too hot for water to absorb enough heat to put out the fire. If water is used to extinguish ("put out") a metal fire, the water will simply evaporate. For metal fires, sand can be used to cover the fire and keep it from obtaining oxygen. A fire extinguisher can put out most fires. Culture
In human culture, fire is often used as a symbol of destruction and anger.
Toxic gases from fires.
The major lethal factors in uncontrolled fires are toxic gases, heat, and oxygen deficiency. The predominant toxic gas is carbon monoxide, which is readily generated from the combusion of wood and other cellulosic materials. Increasing use of a variety of synthetic polymers has stimulated interest in screening tests to evaluated the toxicity of polymeric materials when thermally decomposed. As yet, this country lacks a standardized fire toxicity test protocol.
Published in Science (New York, N.Y.) (1978)
Everything we examined (3) — 2 independent sources
This check searched the claim as stated. It did not run a separate search for evidence against it.