Editing Apollo 1 (section)

==== Ignition source ====
The review board determined that the electrical power momentarily failed at 23:30:55 GMT, and found evidence of several [[electric arc]]s in the interior equipment. They were unable to conclusively identify a single ignition source. They determined that the fire most likely started near the floor in the lower left section of the cabin, close to the Environmental Control Unit.<ref name="aibreport" />{{Reference page|page=6-1}} It spread from the left wall of the cabin to the right, with the floor being affected only briefly.<ref name="aibreport" />{{Reference page|page=5-3}}

The board noted that a silver-plated copper wire, running through an environmental control unit near the center couch, had become stripped of its [[Polytetrafluoroethylene|Teflon]] insulation and abraded by repeated opening and closing of a small access door.{{efn|In 1967 a vice president of North American Aviation, John McCarthy, speculated that Grissom had accidentally "scuffed the insulation of a wire" while moving about the spacecraft, but his remarks were ignored by the review board and strongly rejected by a congressional committee. [[Frank Borman]], who had been the first astronaut to go inside the burned spacecraft, testified, "We found no evidence to support the thesis that Gus, or any of the crew members kicked the wire that ignited the flammables." A 1978 history of the accident written internally by NASA said at the time, "This theory that a scuffed wire caused the spark that led to the fire still has wide currency at Kennedy Space Center. Men differ, however, on the cause of the scuff."<ref name = spaceport>{{Cite book |last1=Benson |first1=Charles D. |url=http://www.hq.nasa.gov/office/pao/History/SP-4204/ch18-6.html |title=Chapter 18-6 – The Fire That Seared The Spaceport, "The Review Board" |last2=Faherty |first2=William Barnaby |publisher=NASA |year=1978 |series=NASA History Series |lccn=77029118 |id=NASA SP-4204 |ref=moonport |access-date=August 5, 2020}}</ref> Soon after making his comment McCarthy had said, "I only brought it up as a hypothesis."<ref>{{Cite magazine |date=April 21, 1967 |title=Blind Spot |magazine=[[Time (magazine)|Time]] |url=http://www.time.com/time/magazine/article/0,9171,843575-2,00.html |archive-url=https://web.archive.org/web/20090114084112/http://www.time.com/time/magazine/article/0,9171,843575-2,00.html |archive-date=January 14, 2009 |access-date=May 21, 2008}}</ref>}}

This weak point in the wiring also ran near a junction in an [[ethylene glycol]]/water cooling line that had been prone to leaks. [[Electrolysis]] of ethylene glycol solution with the silver [[anode]] of the wire was discovered at the [[Manned Spacecraft Center]] on May 29, 1967, to be a hazard capable of causing a violent [[exothermic reaction]], igniting the ethylene glycol mixture in the Command Module's pure oxygen atmosphere. Experiments at the [[Illinois Institute of Technology]] confirmed the hazard existed for silver-plated wires, but not for copper-only or nickel-plated copper. In July, ASPO directed both North American and Grumman to ensure no silver or silver-coated electrical contacts existed in the vicinity of possible glycol spills in the Apollo spacecraft.<ref>{{Cite book |last1=Ertel |first1=Ivan D. |url=http://www.hq.nasa.gov/office/pao/History/SP-4009/contents.htm#Volume%20IV |title=The Apollo Spacecraft: A Chronology |last2=Newkirk |first2=Roland W. |last3=Brooks |first3=Courtney G. |publisher=NASA |year=1969–1978 |volume=IV |location=Washington, D.C. |chapter=Part 2 (B): Recovery, Spacecraft Redefinition, and First Manned Apollo Flight: May 29, 1967 |lccn=69060008 |oclc=23818 |id=NASA SP-4009 |display-authors=2 |access-date=July 12, 2013 |chapter-url=http://www.hq.nasa.gov/office/pao/History/SP-4009/v4p2b.htm |archive-date=February 5, 2008 |archive-url=https://web.archive.org/web/20080205020128/http://www.hq.nasa.gov/office/pao/History/SP-4009/contents.htm#Volume%20IV |url-status=dead }}</ref>