liquid at its melting point and remains in this state until  the  temperature  rises  to  its  boiling  point, –297°F   (–183°C). At  this  latter  temperature,  LOX  vaporizes  into the gaseous state. Gaseous oxygen will turn into liquid  at  atmospheric  pressure  by  cooling  to  a temperature  below  –297°F.  By  increasing  the pressure, gaseous oxygen can be liquified at higher temperatures,   up   to   its   critical   temperature, – 182°F ( –119°C). Oxygen will not condense to a   liquid   at   temperatures   above   its   critical temperature  regardless  of  the  pressure  applied. The  pressure  required  to  liquify  oxygen  at  its critical  temperature  is  known  as  its  critical pressure,   736.5   psig.   The   application   of   high pressure  and  ultra-low  temperatures  to  convert gases to their liquid state is known as the science and technology of cryogenics. LOX is a cryogenic fluid. Physical Properties of Liquid Oxygen Gaseous   oxygen   is   colorless   odorless, tasteless, and about 1.1 times as heavy as air. LOX is  an  extremely  cold,  pale  blue  fluid  that  flows like   water.   One   gallon   of   LOX   weighs   9.519 pounds,  which  is  1.14  times  heavier  than  the weight  of  1  gallon  of  water.  LOX  is  stored  and handled  at  atmospheric  pressure  in  well-insulated containers that maintain the liquid at its boiling point  (  –297°F).  Therefore,  LOX  is  boiling  as  it slowly   turns   into   gaseous   oxygen.   As   the expanding  gas  from  the  boiling  liquid  increases in   amount,   it   builds   up   pressure   within   the container. Therefore, the expanding gas must be vented to the atmosphere. Confinement of liquid oxygen  can  be  dangerous  to  personnel,  causing severe injury and death. This section contains procedures and require- ments  for  the  quality  control  of  LOX  that  is stored,  transferred,  handled,  and  used  for breathing   purposes   by   aircrews.   This   section applies to AME supervisors who must ensure all safety  procedures  and  equipment  are  used  during LOX   servicing   and   handling   by   qualified personnel. Personnel Personnel  selected  to  perform  operations  in the  LOX  supply  system  should  be  trained  and have a thorough knowledge of the characteristics of  LOX,  the  significance  of  contamination,  and the dangers involved. Only those personnel who demonstrate  understanding  of  safety  and  who maintain  reliable  performance  should  be  assigned the duties and responsibilities of handling LOX. LOX Contamination During  the  handling  and  transfer  of  LOX, environmental  contaminants  must  be  prevented from entering the system. LOX strongly attracts and  absorbs  atmospheric  gases.  Contaminants make the ABO unusable. Conscientious attention to  correct  procedures  during  handling  and  transfer operations  will  prevent  contamination  and  ensure safety. The aircraft LOX converter system should be sampled and tested for contamination as follows: Test  for  odor  as  soon  as  possible  after  a  report of  in-flight  odors  by  the  pilot  or  aircrew.  Any abnormal  psychological  or  physiological  effects to an aircrew during or after flight should be cause to   suspect   possible   oxygen   contamination. Possible  oxygen  contamination  should  also  be considered  in  any  aircraft  mishap  when  the circumstances  of  the  mishap  are  vague  or unknown. A sample should be taken and sent to a test site for analysis with supporting details of the incident, including history of the supply source of LOX. Appropriate reports must be submitted in  accordance  with  OPNAVINST  3750.6.  An information copy should be provided to the Naval Air  Engineering  Center  program  manager. Applicable   squadrons   selected   by   area commands  must,  during  each  calender  month, take  a  LOX  sample  from  at  least  one  filled converter  and  residual  LOX  from  one  converter (taken from an aircraft after a flight mission), and forward  both  to  a  test  site  for  contamination checks. Aircraft  oxygen  and  LOX  systems,  and  LOX converters,  must  be  purged  in  accordance  with  the applicable   maintenance   instructions   manual (MIM)   and/or   NAVAIR   13-1-6.4,   O x y g en Equipment  Manual.  Purging  is  done  when  the system  or  the  converter  is  left  open  to  the atmosphere, when   empty,   or   whenever contamination  is  suspected. GASEOUS   OXYGEN The  supervision  of  aviators  gaseous  breathing oxygen requires the same surveillance as for LOX. Adequate   and   reliable   supervisory   control   of aviators gaseous breathing oxygen demands that each operation in the gaseous breathing oxygen supply, and aircraft servicing system, be carried 1-5