Editing Oxygen (section)

==Safety and precautions==
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The [[NFPA 704]] standard rates compressed oxygen gas as nonhazardous to health, nonflammable and nonreactive, but an oxidizer. Refrigerated liquid oxygen (LOX) is given a health hazard rating of 3 (for increased risk of [[hyperoxia]] from condensed vapors, and for hazards common to cryogenic liquids such as frostbite), and all other ratings are the same as the compressed gas form.<ref name="nfpa">{{cite web|url = http://www.rivcoeh.org/Portals/0/documents/guidance/hazmat/bep_nfparatings.pdf|publisher = Riverside County Department of Environmental Health|access-date = August 22, 2017|title = NFPA 704 ratings and id numbers for common hazardous materials|archive-date = July 11, 2019|archive-url = https://web.archive.org/web/20190711171240/http://www.rivcoeh.org/Portals/0/documents/guidance/hazmat/bep_nfparatings.pdf|url-status = live}}</ref>

===Toxicity===
{{Main|Oxygen toxicity}}
[[File:Symptoms of oxygen toxicity.png|thumb|left|upright=1.35|Main symptoms of oxygen toxicity<ref>{{cite journal |author=Dharmeshkumar N Patel |display-authors=4 |author2=Ashish Goel |author3=SB Agarwal |author4=Praveenkumar Garg |author5=Krishna K Lakhani |title=Oxygen Toxicity |journal=Indian Academy of Clinical Medicine |volume=4 |issue=3 |page=234 |date=2003 |url=http://medind.nic.in/jac/t03/i3/jact03i3p234.pdf |access-date=April 26, 2009 |archive-date=September 22, 2015 |archive-url=https://web.archive.org/web/20150922093352/http://medind.nic.in/jac/t03/i3/jact03i3p234.pdf |url-status=dead }}</ref>|alt=A diagram showing a male torso and listing symptoms of oxygen toxicity: Eyes&nbsp;– visual field loss, nearsightedness, cataract formation, bleeding, fibrosis; Head&nbsp;– seizures; Muscles&nbsp;– twitching; Respiratory system&nbsp;– jerky breathing, irritation, coughing, pain, shortness of breath, tracheobronchitis, acute respiratory distress syndrome.]]

Oxygen gas ({{chem|O|2}}) can be [[Oxygen toxicity|toxic]] at elevated [[partial pressure]]s, leading to [[convulsion]]s and other health problems.<ref name="Acott" /><ref group=lower-alpha>Since {{chem|O|2}}'s partial pressure is the fraction of {{chem|O|2}} times the total pressure, elevated partial pressures can occur either from high {{chem|O|2}} fraction in breathing gas or from high breathing gas pressure, or a combination of both.</ref><ref name="ECE511">[[#Reference-idCook1968|Cook & Lauer 1968]], p. 511</ref> Oxygen toxicity usually begins to occur at partial pressures more than 50 kilo[[Pascal (unit)|pascals]]&nbsp;(kPa), equal to about 50% oxygen composition at standard pressure or 2.5 times the normal sea-level {{chem|O|2}} partial pressure of about 21&nbsp;kPa. This is not a problem except for patients on [[mechanical ventilator]]s, since gas supplied through [[oxygen mask]]s in medical applications is typically composed of only 30–50% {{chem|O|2}} by volume (about 30&nbsp;kPa at standard pressure).<ref name="NBB299" />

At one time, [[Premature birth|premature babies]] were placed in incubators containing {{chem|O|2}}-rich air, but this practice was discontinued after some babies were blinded by the oxygen content being too high.<ref name="NBB299" />

Breathing pure {{chem|O|2}} in space applications, such as in some modern space suits, or in early spacecraft such as [[Apollo spacecraft|Apollo]], causes no damage due to the low total pressures used.<ref name="pmid11541018" /><ref>{{cite web|last = Wade|first = Mark|date = 2007|url = http://www.astronautix.com/craftfam/spasuits.htm|title = Space Suits|publisher = Encyclopedia Astronautica |access-date=December 16, 2007 |url-status = dead|archive-url = https://web.archive.org/web/20071213122134/http://www.astronautix.com/craftfam/spasuits.htm |archive-date = December 13, 2007}}</ref> In the case of spacesuits, the {{chem|O|2}} partial pressure in the breathing gas is, in general, about 30&nbsp;kPa (1.4 times normal), and the resulting {{chem|O|2}} partial pressure in the astronaut's arterial blood is only marginally more than normal sea-level {{chem|O|2}} partial pressure.<ref>{{cite web |url=http://www.globalrph.com/martin_4_most2.htm |title=The Four Most Important Equations In Clinical Practice |last=Martin |first=Lawrence |website=GlobalRPh |publisher=David McAuley |access-date=June 19, 2013 |archive-date=September 5, 2018 |archive-url=https://web.archive.org/web/20180905215615/http://www.globalrph.com/martin_4_most2.htm |url-status=live }}</ref>

Oxygen toxicity to the lungs and [[central nervous system]] can also occur in deep [[scuba diving]] and [[surface-supplied diving]].<ref name="NBB299" /><ref name="Acott" /> Prolonged breathing of an air mixture with an {{chem|O|2}} partial pressure more than 60&nbsp;kPa can eventually lead to permanent [[pulmonary fibrosis]].<ref name="BMJ">{{cite journal |author=Wilmshurst P |title=Diving and oxygen |journal=BMJ |volume=317 |issue=7164 |pages=996–99 |date=1998 |pmid=9765173 |pmc=1114047 |doi=10.1136/bmj.317.7164.996}}</ref> Exposure to an {{chem|O|2}} partial pressure greater than 160&nbsp;kPa (about 1.6 atm) may lead to convulsions (normally fatal for divers). Acute oxygen toxicity (causing seizures, its most feared effect for divers) can occur by breathing an air mixture with 21% {{chem|O|2}} at {{convert|66|m|abbr=on}} or more of depth; the same thing can occur by breathing 100% {{chem|O|2}} at only {{convert|6|m|abbr=on}}.<ref name="BMJ" /><ref name="Donald">{{cite book |last=Donald |first=Kenneth |title=Oxygen and the Diver |isbn = 978-1-85421-176-7|date=1992 |publisher=SPA in conjunction with K. Donald |location=England}}</ref><ref name="Donald1">{{cite journal |author=Donald K. W. |title=Oxygen Poisoning in Man: Part I |journal=Br Med J |volume=1 |issue=4506 |pages=667–72 |date=1947 |pmc=2053251 |doi=10.1136/bmj.1.4506.667 |pmid=20248086}}</ref><ref name="Donald2">{{cite journal |author=Donald K. W. |title=Oxygen Poisoning in Man: Part II |journal=Br Med J |volume=1 |pages=712–17 |date=1947 |pmc=2053400|issue=4507 |doi=10.1136/bmj.1.4507.712 |pmid=20248096}}</ref>

===Combustion and other hazards===
[[File:Apollo 1 fire.jpg|thumb|right|The interior of the [[Apollo 1]] Command Module. Pure {{chem|O|2}} at higher than normal pressure and a spark led to a fire and the loss of the Apollo 1 crew.|alt=The inside of a small spaceship, charred and apparently destroyed.]]
Highly concentrated sources of oxygen promote rapid combustion. Fire and [[explosion]] hazards exist when concentrated oxidants and [[fuel]]s are brought into close proximity; an ignition event, such as heat or a spark, is needed to trigger combustion.<ref name="astm-tpt"/> Oxygen is the oxidant, not the fuel.

Concentrated {{chem|O|2}} will allow combustion to proceed rapidly and energetically.<ref name="astm-tpt" /> 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 {{chem|O|2}} systems requires special training to ensure that ignition sources are minimized.<ref name="astm-tpt" /> The fire that killed the [[Apollo 1]] crew in a launch pad test spread so rapidly because the capsule was pressurized with pure {{chem|O|2}} but at slightly more than atmospheric pressure, instead of the {{frac|1|3}} normal pressure that would be used in a mission.{{refn|No single ignition source of the fire was conclusively identified, although some evidence points to an arc from an electrical spark.<ref>Report of Apollo 204 Review Board NASA Historical Reference Collection, NASA History Office, NASA HQ, Washington, DC</ref>|group=lower-alpha}}<ref name="chiles">{{cite book|last=Chiles|first=James R.|date=2001|title=Inviting Disaster: Lessons from the edge of Technology: An inside look at catastrophes and why they happen|url=https://archive.org/details/invitingdisaster00jame|url-access=registration|location=New York|publisher=HarperCollins Publishers Inc.|isbn=978-0-06-662082-4}}</ref>

Liquid oxygen spills, if allowed to soak into organic matter, such as [[wood]], [[petrochemical]]s, and [[Bitumen|asphalt]] can cause these materials to [[Detonation|detonate]] unpredictably on subsequent mechanical impact.<ref name="astm-tpt" />
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