Editing Apollo 1 (section)

== Choice of pure oxygen atmosphere ==
When designing the Mercury spacecraft, NASA had considered using a nitrogen/oxygen mixture to reduce the fire risk near launch, but rejected it based on a number of considerations. First, a pure oxygen atmosphere is comfortably breathable by humans at {{convert|5|psi|kPa|abbr=on}}, greatly reducing the pressure load on the spacecraft in the vacuum of space. Second, nitrogen used with the in-flight pressure reduction carried the risk of [[decompression sickness]] (known as "the bends"). But the decision to eliminate the use of any gas but oxygen was criticized when a serious accident occurred on April 21, 1960, in which [[McDonnell Aircraft]] test pilot G. B. North passed out and was seriously injured when testing a Mercury cabin / spacesuit atmosphere system in a vacuum chamber. The problem was found to be nitrogen-rich (oxygen-poor) air leaking from the cabin into his spacesuit feed.<ref>{{Cite journal |last=Giblin |first=Kelly A. |date=Spring 1998 |title=Fire in the Cockpit! |url=http://www.americanheritage.com/articles/magazine/it/1998/4/1998_4_46.shtml |journal=[[American Heritage of Invention & Technology]] |publisher=American Heritage Publishing |volume=13 |issue=4 |archive-url=https://web.archive.org/web/20081120153024/http://www.americanheritage.com/articles/magazine/it/1998/4/1998_4_46.shtml |archive-date=November 20, 2008 |access-date=March 23, 2011}}</ref> North American Aviation had suggested using an oxygen/nitrogen mixture for Apollo, but NASA overruled this. The pure oxygen design was judged to be safer, less complicated, and lighter in weight.<ref name="chariots9-3">{{Cite book |last1=Brooks |first1=Courtney G. |url=https://history.nasa.gov/SP-4205/cover.html |title=Chariots for Apollo: A History of Manned Lunar Spacecraft |last2=Grimwood |first2=James M. |last3=Swenson |first3=Loyd S. Jr. |publisher=Scientific and Technical Information Branch, NASA |others=Foreword by [[Samuel C. Phillips]] |year=1979 |isbn=0-486-46756-2 |series=NASA History Series |location=Washington, D.C. |chapter=The Investigation |oclc=4664449 |id=NASA SP-4205 |access-date=January 6, 2016 |chapter-url=http://www.hq.nasa.gov/office/pao/History/SP-4205/ch9-3.html}}</ref> In his monograph ''Project Apollo: The Tough Decisions'', Deputy Administrator Seamans wrote that NASA's worst mistake in engineering judgment was not running a fire test on the command module before the plugs-out test.<ref name="toughDecisions">{{Cite book |last=Seamans |first=Robert C. Jr. |url=https://history.nasa.gov/monograph37.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://history.nasa.gov/monograph37.pdf |archive-date=October 9, 2022 |url-status=live |title=Project Apollo: The Tough Decisions |publisher=NASA |year=2005 |isbn=978-0-16-074954-4 |series=Monographs in Aerospace History |volume=37 |location=Washington, DC|pages=76–77 |lccn=2005003682 |id=NASA SP-2005-4537 |access-date=July 14, 2013}}</ref> In the first episode of the 2009 [[BBC]] documentary series ''NASA: Triumph and Tragedy'', [[James McDivitt|Jim McDivitt]] said that NASA had no idea how a 100% oxygen atmosphere would influence burning.<ref>{{Cite episode|title=One Small Step|series=NASA: Triumph and Tragedy|date=2009|publisher=BBC|url=https://www.bbc.co.uk/programmes/b00lg2xb|access-date=June 4, 2023}}</ref> Similar remarks by other astronauts were expressed in the 2007 documentary film [[In the Shadow of the Moon (2007 film)|''In the Shadow of the Moon'']].<ref name="Sundance">{{cite web| url = http://festival.sundance.org/filmguide/popup.aspx?film=3316| archive-url = https://web.archive.org/web/20071218040021/http://festival.sundance.org/filmguide/popup.aspx?film=3316| archive-date = December 18, 2007| title = In the Shadow of the Moon| access-date = April 8, 2007| work = World Documentary Competition| publisher = [[Sundance Film Festival]]}}</ref>

=== Other oxygen incidents ===
Several fires in high-oxygen test environments had occurred before the Apollo fire. In 1962, [[United States Air Force|USAF]] Colonel B. Dean Smith was conducting a test of the [[Gemini space suit]] with a colleague in a pure oxygen chamber at [[Brooks Air Force Base]] in [[San Antonio]], Texas, when a fire broke out, destroying the chamber. Smith and his partner narrowly escaped.<ref>{{Cite book |last=Smith |first=B. Dean |title=The Fire That NASA Never Had |publisher=[[PublishAmerica]] |year=2006 |isbn=978-1-4241-2574-6 |location=Baltimore, MD |lccn=2006297829 | ol=9777501W | oclc=71290504 }}</ref> On November 17, 1962, a fire broke out in a chamber at the Navy's Air Crew Equipment Laboratory during a pure oxygen test. The fire was started because a faulty ground wire arced onto nearby insulation. After attempts to extinguish the fire by smothering it, the crew escaped the chamber with minor burns across large parts of their bodies.<ref>{{Cite web|title=Navy Air Crew Equipment Laboratory, November 17, 1962|url=https://history.nasa.gov/Apollo204/appendices/AppendixD1-4.pdf|access-date=February 23, 2023|website=Apollo 204 Review Board Final Report|publisher=NASA|page=D-2–25}}</ref> On February 16, 1965, [[Navy diver (United States Navy)|United States Navy Divers]] Fred Jackson and John Youmans were killed in a [[decompression chamber]] fire at the [[United States Navy Experimental Diving Unit|Experimental Diving Unit]] in [[Washington, D.C.]], shortly after additional oxygen was added to the chamber's atmospheric mix.<ref>{{Cite web |title=Navy Experimental Diving Unit, February 16, 1965 |url=https://history.nasa.gov/Apollo204/appendices/AppendixD1-4.pdf |access-date=August 20, 2018 |website=Apollo 204 Review Board Final Report |publisher=NASA |pages=D-2-24–D-2-25}}</ref><ref>{{Cite book |last=Hellwarth |first=Ben |url=https://archive.org/details/sealabamericasfo0000hell |title=Sealab: America's Forgotten Quest to Live and Work on the Ocean Floor |publisher=[[Simon & Schuster]] |year=2012 |isbn=978-0-7432-4745-0 |location=New York |pages=[https://archive.org/details/sealabamericasfo0000hell/page/126 126]–127 |lccn=2011015725 |url-access=registration}}</ref>

In addition to fires with personnel present, the Apollo Environmental Control System experienced several accidents from 1964 to 1966 due to various hardware malfunctions. Notable is the April 28, 1966, fire, as the subsequent investigation found that several new measures should be taken to avoid fires, including improved selection of materials and that ESC and Command Module circuits have a potential for arcing or short circuits.<ref>{{Cite web|title=Apollo ECS Fire at Airsearch Torrance Facility, April 28, 1966|url=https://history.nasa.gov/Apollo204/appendices/AppendixD1-4.pdf|website=Apollo 204 Review Board Final Report|publisher=NASA|pages=D-2-25–D-2-26}}</ref>

Other oxygen fire occurrences are documented in reports archived in the [[National Air and Space Museum]],<ref>{{Cite web |year=2001 |title=Bellcomm, Inc Technical Library Collection |url=http://www.nasm.si.edu/research/arch/findaids/bellcomm/bci_print.html |access-date=April 5, 2010 |website=National Air and Space Museum |publisher=Smithsonian Institution |location=Washington, D.C. |id=Accession No. XXXX-0093 |archive-date=April 9, 2010 |archive-url=https://web.archive.org/web/20100409090552/http://nasm.si.edu/research/arch/findaids/bellcomm/bci_print.html |url-status=dead }}</ref> such as:
* Selection of Space Cabin Atmospheres. Part II: Fire and Blast Hazards {{sic}} in Space Cabins. (Emanuel M. Roth; Dept of Aeronautics Medicine and Bioastronautics, Lovelace Foundation for Medical Education and Research. c. 1964–1966)
* "Fire Prevention in Manned Spacecraft and Test Chamber Oxygen Atmospheres". ([[Manned Spacecraft Center]]. NASA General Working Paper 10 063. October 10, 1966)

Incidents had also occurred in the [[Soviet space program]], but due to the Soviet government's policy of secrecy, these were not disclosed until well after the Apollo{{nbsp}}1 fire. [[Cosmonaut]] [[Valentin Bondarenko]] died on March 23, 1961, from burns sustained in a fire while participating in a 15-day endurance experiment in a high-oxygen isolation chamber, less than three weeks before the first [[Vostok programme|Vostok]] crewed space flight; this was disclosed on January 28, 1986.<ref name="siddiqi2000">{{Cite book |last=Siddiqi |first=Asif A. |title=Challenge to Apollo: The Soviet Union and the Space Race, 1945–74 |publisher=[[NASA|NASA History Division]]  |year=2000 |page=266 |lccn=00038684 |author-link=Asif Azam Siddiqi  |url=https://history.nasa.gov/SP-4408pt1.pdf |id=NASA SP-2000-4408 |archive-url=https://web.archive.org/web/20220415164521/https://history.nasa.gov/SP-4408pt1.pdf |archive-date=April 15, 2022 |url-status=live }}</ref><ref>{{Cite book |last1=Hall |first1=Rex D. |url=https://archive.org/details/russiascosmonaut00hall |title=Russia's Cosmonauts: Inside the Yuri Gagarin Training Center |last2=Shayler |first2=David J. |last3=Vis |first3=Bert |publisher=Springer |year=2005 |isbn=0-387-21894-7 |location=Chichester, UK |pages=[https://archive.org/details/russiascosmonaut00hall/page/n107 75]–77 |lccn=2005922814 |url-access=limited}}</ref><ref>{{Cite book |last1=Scott |first1=David |url=https://archive.org/details/twosidesofmoon00scot |title=Two Sides of the Moon: Our Story of the Cold War Space Race |last2=Leonov |first2=Alexei |last3=Toomey |first3=Christine |publisher=[[Thomas Dunne Books]] |others=Foreword by [[Neil Armstrong]]; introduction by [[Tom Hanks]] |year=2004 |isbn=0-312-30865-5 |edition=1st U.S. |location=New York |lccn=2004059381 |oclc=56587777 |author-link=David Scott |author-link2=Alexey Leonov}}</ref>

During the [[Voskhod 2]] mission in March 1965, cosmonauts [[Pavel Belyayev]] and [[Alexei Leonov]] could not completely seal the spacecraft hatch after Leonov's historic first [[extravehicular activity|walk in space]]. The spacecraft's environmental control system responded to the leaking air by adding more oxygen to the cabin, causing the concentration level to rise as high as 45%. The crew and ground controllers worried about the possibility of fire, remembering Bondarenko's death four years earlier.<ref name=siddiqi2000 />{{Reference page|page=457}}

On January 31, 1967, four days after the Apollo{{nbsp}}1 fire, United States Air Force airmen William F. Bartley Jr. and Richard G. Harmon were killed in a flash fire while tending laboratory rabbits in the Two Man Space Environment Simulator, a pure oxygen chamber at the School of Aerospace Medicine at Brooks Air Force Base.<ref>{{Cite web |title=Brooks Air Force Base, January 31, 1967 |url=https://history.nasa.gov/Apollo204/appendices/AppendixD1-4.pdf |access-date=August 20, 2018 |website=Apollo 204 Review Board Final Report |publisher=NASA |pages=D-2-23–D-2-24}}</ref><ref>{{Cite web |title=The Apollo Spacecraft – A Chronology. Vol. IV. Part 1 (1967 Jan) |url=https://www.hq.nasa.gov/pao/History/SP-4009/v4p1e.htm |access-date=August 20, 2018 |publisher=NASA |archive-date=March 8, 2021 |archive-url=https://web.archive.org/web/20210308084736/https://www.hq.nasa.gov/pao/History/SP-4009/v4p1e.htm |url-status=dead }}</ref><ref>{{Cite book |last=Flynn |first=Thomas M. |url=https://books.google.com/books?id=-XfMBQAAQBAJ&pg=PA798 |title=Cryogenic Engineering |publisher=[[CRC Press]] |year=2004 |isbn=978-0-203-02699-1 |edition=Second |page=798}}</ref><ref>{{Cite book |url=https://books.google.com/books?id=B4LgBwAAQBAJ&pg=PA648 |title=The Underwater Handbook: A Guide to Physiology and Performance for the Engineer |publisher=[[Springer Science+Business Media]] |year=2013 |isbn=978-1-4684-2156-9 |editor-last=Shilling |editor-first=Charles W. |editor-link=Charles Wesley Shilling |page=648 |editor-last2=Werts |editor-first2=Margaret F. |editor-last3=Schandelmeier |editor-first3=Nancy R.}}</ref><ref name="Orcutt">{{Cite news |last=Orcutt |first=David |date=March 31, 2017 |title=Orcutt: Remembering the SAM tragedy, a swell |work=[[The Roanoke Times]] |url=https://www.roanoke.com/opinion/commentary/orcutt-remembering-the-sam-tragedy-a-swell/article_59194738-a47d-56d4-b77d-6ab9f934fe1c.html |access-date=August 20, 2018}}</ref> Like the Apollo{{nbsp}}1 fire, the School fire was caused by an electrical spark in a pure oxygen environment. The widows of the Apollo{{nbsp}}1 crew sent condolence letters to Bartley and Harmon's families.<ref name="Orcutt" />