Methods and apparatus to generate liquid ambulatory oxygen from an oxygen concentrator

• US RE43,398 E1
• Filed: 03/01/2006
• Issued: 05/22/2012
• Est. Priority Date: 06/16/1997
• Status: Expired due to Term

• Current Assignee: Respironics Incorporated
• Original Assignee: Respironics Incorporated
• Inventors: Hill, Theodore B., Walker, Graham, Honkonen, Scott C., Hill, Charles C.
• Primary Examiner(s): Dixon, Annette
• Application Number:
  US11/366,986
• Time in Patent Office: 2,274 Days
• Field of Search: 128/200.24, 128/201.21, 128/204.15, 128/204.17, 128/203.25, 128/203.26, 128/203.27, 128/204.22, 128/204.23, 128/913, 128/DIG.27, 626/06, 626/15, 165/110, 165/174
• US Class Current: 128/201.21
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/116 Molecular sieves other than zeolites
• CPC Class Codes: B01D 2256/12 Oxygen
• CPC Class Codes: B01D 2257/102 Nitrogen
• CPC Class Codes: B01D 2257/404 Nitrogen oxides other than dinitrogen oxide
• CPC Class Codes: B01D 2257/502 Carbon monoxide
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2257/80 Water
• CPC Class Codes: B01D 2259/40001 Methods relating to additional, e.g. intermediate, treatment of process gas
• CPC Class Codes: B01D 2259/40009 using sensors or gas analysers
• CPC Class Codes: B01D 2259/416 involving cryogenic temperature treatment
• CPC Class Codes: B01D 2259/4525 for storage and dispensing systems
• CPC Class Codes: B01D 2259/4533 for medical purposes
• CPC Class Codes: B01D 2259/4541 for portable use, e.g. gas masks
• CPC Class Codes: B01D 2259/455 for transportable use portable devices B01D2259/4541
• CPC Class Codes: B01D 5/0039 Recuperation of heat, e.g. use of heat pump(s), compression
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: B01D 53/053 with storage or buffer vessel
• CPC Class Codes: B01D 53/261 by adsorption
• CPC Class Codes: F17C 2221/011 Oxygen
• CPC Class Codes: F17C 2223/0161 : cryogenic, e.g. LNG, GNL, PLNG
• CPC Class Codes: F17C 2227/0353 : using cryocooler
• CPC Class Codes: F17C 2265/015 : by separating
• CPC Class Codes: F17C 2270/0509 : "Dewar" vessels
• CPC Class Codes: F17C 6/00 : Methods and apparatus for filling vessels not under pressure with liquefied or solidified gases
• CPC Class Codes: F25B 9/006 : the refrigerant containing more than one component F25B9/004 takes precedence
• CPC Class Codes: F25B 9/145 : pulse-tube cycle
• CPC Class Codes: F25J 1/0017 : Oxygen
• CPC Class Codes: F25J 1/0052 : by vaporising a liquid refrigerant stream
• CPC Class Codes: F25J 1/0212 : as a single flow MCR cycle
• CPC Class Codes: F25J 1/0225 : using other external refrigeration means not provided before, e.g. heat driven absorption chillers
• CPC Class Codes: F25J 1/0244 : Operation; Control and regulation; Instrumentation F25J1/0279 takes precedence
• CPC Class Codes: F25J 1/0276 : Laboratory or other miniature devices
• CPC Class Codes: F25J 2205/40 : using hybrid system, i.e. combining cryogenic and non-cryogenic separation techniques
• CPC Class Codes: F25J 2205/60 : using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
• CPC Class Codes: F25J 2205/80 : using membrane, i.e. including a permeation step
• CPC Class Codes: F25J 2210/40 : Air or oxygen enriched air, i.e. generally less than 30mol% of O2
• CPC Class Codes: F25J 2220/50 : Separating low boiling, i.e. more volatile components from oxygen, e.g. N2, Ar
• CPC Class Codes: F25J 2270/90 : External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
• CPC Class Codes: F25J 2270/91 : using pulse tube refrigeration
• CPC Class Codes: Y02C 10/08 : Capture by adsorption
• CPC Class Codes: Y02P 70/34 : relating to separation, flotation or differential sedimentation

Abstract

The present invention is directed to a much safer and less expensive way of providing portable oxygen from a gas concentrator for patients who do not want to be tied to a stationary machine or restricted by present oxygen technology. The present invention involves a home liquid oxygen ambulatory system for supplying a portable supply of oxygen, where a portion of the gaseous oxygen output obtained from an oxygen concentrator is condensed into liquid oxygen. The system includes an oxygen concentrator which separates oxygen gas from the ambient air, a condenser in communication with the oxygen concentrator for receiving and liquefying the oxygen gas flow, a cryocooler associated with the condenser, and a first storage dewar in fluid communication with the condenser and adapted to store the oxygen liquefied by the condenser, the first storage dewar including means for transferring liquid oxygen from the first dewar to a second dewar for storing a quantity of oxygen suitable for moveable oxygen treatment.

Claims

1. A home liquid oxygen ambulatory system for supplying a portable supply of oxygen, where a portion of the gaseous oxygen output obtained from an oxygen concentrator a pressure swing adsorption system is condensed into liquid oxygen, comprising:

(a) an oxygen concentrator a pressure swing adsorption system comprising a molecular sieve bed which separates oxygen gas from receives the ambient air as an input and provides an output of oxygen-enriched gas;

(b) a condenser in communication with said oxygen concentrator pressure swing adsorption system for receiving and liquefying the oxygen gas flow the output from the pressure swing adsorption system;

(c) a cryocooler associated with said condenser; and

(d) a first storage dewar in fluid communication with said condenser and adapted to store the oxygen liquefied by the condenser, the first storage dewar including means for transferring liquid oxygen from the first dewar to a second dewar for storing a quantity of oxygen suitable for moveable oxygen treatment, wherein said liquid oxygen transferring means is adapted to increase the pressure in said first dewar.

2. The system of claim 1, wherein said liquid transferring means includes a heater immersed within the liquid oxygen in said first dewar.

3. The system of claim 1, wherein said first dewar includes an inner vessel in which said liquid oxygen reside, and liquid transferring means includes a heater attached to the outer surface of inner vessel.

4. The system of claim 1, wherein said condenser is in communication with said concentrator pressure swing adsorption system through a line, and said liquid transferring means includes a compressor located in said line between said condenser and said concentrator pressure swing adsorption system.

5. The system of claim 1, wherein said liquid transferring means includes a high-pressure compressor in communication with said concentrator for delivering high-pressure air thereto.

6. The system of claim 1, wherein said liquid transferring means includes a vaporizer loop associated with said first dewar.

7. The system of claim 1, wherein said liquid transferring means includes a controllable heat leak associated with said first dewar.

8. The system of claim 1, wherein said liquid transferring means includes a gravity-assisted dispensing mechanism.

9. The system of claim 1, wherein said system further includes said second storage dewar and said second storage dewar is adapted to be filled at a pressure below 20 psig.

10. A method for generating liquid oxygen in a home from a home liquid oxygen ambulatory system having an oxygen concentrator a pressure swing adsorption system comprising a molecular sieve bed, a condenser, and cryocooler, a storage dewar and means for transferring liquid oxygen from the first dewar to a second dewar, comprising:

(a) generating a gaseous supply of oxygen using the oxygen concentrator pressure swing adsorption system which receives the ambient air as an input and provides an output of oxygen-enriched gas;

(b) splitting off at least a portion of the gaseous supply to be liquefied;

(c) cooling said supply of oxygen using the condenser and cryocooler to transform the gaseous oxygen to liquid oxygen;

(d) storing the liquid oxygen in the storage dewar;

(e) transferring the liquid oxygen in the storage dewar with the liquid oxygen transferring means to a second dewar by increasing the pressure in said first dewar for storing a quantity of liquid oxygen from which smaller quantities can be transferred for moveable oxygen treatment.

11. The method of claim 10, wherein said liquid transferring means includes a heater immersed within the liquid oxygen in said first dewar and transferring the liquid oxygen includes heating the liquid oxygen in said first dewar so that the pressure is increased in said first dewar.

12. The method of claim 10, wherein said first dewar includes an inner vessel in which said liquid oxygen reside, said liquid transferring means includes a heater attached to the outer surface of inner vessel, and transferring the liquid oxygen includes heating the liquid oxygen in said first dewar so that the pressure is increased in said first dewar.

13. The method of claim 10, wherein said condenser is in communication with said concentrator pressure swing adsorption system through a line, and said liquid transferring means includes a compressor located in said line between said condenser and said concentrator pressure swing adsorption system, and transferring the liquid oxygen includes increasing the pressure of gaseous oxygen entering said condenser and said dewar with said compressor.

14. The method of claim 10, wherein said liquid transferring means includes a high-pressure compressor in communication with said concentrator for delivering high-pressure air thereto, and transferring the liquid oxygen includes increasing the pressure of gaseous oxygen entering said condenser and said dewar with said compressor.

15. The method of claim 10, wherein said liquid transferring means includes a vaporizer loop associated with said first dewar, and transferring the liquid oxygen includes heating the liquid oxygen in said first dewar with said vaporizer loop so that the pressure is increased in said first dewar.

16. The method of claim 10, wherein said liquid transferring means includes a controllable heat leak associated with said first dewar, and transferring the liquid oxygen includes heating the liquid oxygen in said first dewar so that the pressure is increased in said first dewar.

17. The method of claim 10, wherein said liquid transferring means includes a gravity-assisted dispensing mechanism.

18. The method of claim 10, wherein said system further includes said second storage dewar, said second storage dewar is adapted to filled at a pressure below 20 psig.

19. A liquefier for a home liquid oxygen ambulatory system that is resistant to plugging, the home liquid oxygen ambulatory system having an oxygen concentrator a pressure swing adsorption system comprising a molecular sieve bed for delivering gaseous flow to the liquefier and a storage dewar having an inner vessel for storing liquid oxygen produced by the liquefier, comprising:

a condenser;

a refrigerating mechanism associated with said condenser;

means for communicating incoming gaseous flow from the oxygen concentrator pressure swing adsorption system which receives the ambient air as an input and provides an output of oxygen-enriched gas to the condenser, said communicating means having an inner surface with a dimension D;

means for venting gaseous flow not condensed from the inner vessel, said venting means having an outer surface with a dimension d and disposed within said communicating means; and

whereby the dimension D of the inner surface of the communicating means is significantly larger than the dimension d of the outer surface of the venting means to allow for the build-up of solid contaminants on the outer surface of the venting means without plugging up the communicating means.

20. The liquefier of claim 19, wherein said venting means includes a recuperator comprised of a helical coil of tubing, the tubing having said outer surface with a diameter of said dimension d, whereby the incoming gas stream flows over the outer surface of said helical coil of tubing and a vent stream flows inside said helical coil of tubing.

21. The liquefier of claim 20, wherein said outer surface of said helical coil of tubing has a cold surface to freeze out trace impurities of solid contaminants such as H₂O, CO₂ and hydrocarbons.

22. The liquefier of claim 19, wherein said communicating means is comprised of a neck tube having said inner surface with a diameter of said dimension D.

23. The liquefier of claim 19, wherein refrigerating mechanism is integral with the condenser.

24. The liquefier of claim 19, wherein the refrigerating mechanism and condenser are integral with said storage dewar.

25. A method for generating liquid oxygen in a home from a home liquid oxygen ambulatory system having an oxygen concentrator a pressure swing adsorption system comprising a molecular sieve bed, a condenser, a cryocooler, a recuperator and a storage dewar, comprising:

(a) generating a gaseous supply of oxygen, which includes some trace impurities, using the oxygen concentrator pressure swing adsorption system which receives the ambient air as an input and provides an output of the gaseous supply of oxygen;

(b) splitting off at least a portion of the gaseous supply to be liquefied;

(c) cooling said supply of oxygen using the condenser and cryocooler to transform the gaseous oxygen to liquid oxygen;

(d) condensing less than all of the gaseous oxygen supply flowing into the condenser;

(e) freezing out the trace impurities of the gaseous supply of oxygen and venting the excess gaseous oxygen with said recuperator;

(f) storing the liquid oxygen in the storage dewar; and

(g) periodically removing accumulated frozen impurities on said recuperator by boiling-off any stored liquid oxygen and then flow purging the system until the system has reached room temperature.

26. A generally vertically oriented, gravity assisted condenser for use with a refrigerating mechanism to liquefy gaseous oxygen in a home liquid oxygen ambulatory system, comprising:

a generally vertically oriented tubular member adapted to conduct heat axially to said refrigerating mechanism, the tubular member having a geometric center and outer and inner surfaces, at least one of said outer and inner surfaces having a plurality of generally vertically oriented flutes and convex fins adapted to increase the condensation rate per unit area by thinning the liquid film and drain the condensate to keep the condensate from flooding the condensation surfaces, wherein the flutes and convex fins are circumferentially spaced with respect to each other and not radially aligned with each other relative to the geometric center of the tubular member.

27. The condenser of claim 26, wherein the fins have a hyperbolic cosine profile.

28. The condenser of claim 26, wherein said plurality of generally vertically oriented flutes and convex fins are located on said inner surface.

29. The condenser of claim 26, wherein said plurality of generally vertically oriented flutes and convex fins are located on both said outer and inner surfaces.

30. A generally vertically oriented, gravity assisted condenser for use with a refrigerating mechanism to liquefy gaseous oxygen in a home liquid oxygen ambulatory system, comprising:

a generally vertically oriented tubular member adapted to conduct heat axially to said refrigerating mechanism, the tubular member having outer and inner surfaces, at least one of said outer and inner surfaces includes means for enhancing the condensation rate per unit area by maintaining a small liquid film thickness on the condensation surfaces, said condensation enhancing means including a plurality of generally vertically oriented flutes and convex fins located on both said outer and inner surfaces.

31. An apparatus for supplying oxygen-enriched gas to a patient in a home environment and for use in an ambulatory environment, comprising:

a compressor adapted to receive ambient air and produce compressed air;

a pressure swing adsorption system comprising a molecular sieve bed adapted to produce oxygen-enriched gas, the pressure swing adsorption system having an inlet adapted to receive the compressed air from the compressor and an outlet adapted to provide the oxygen-enriched gas;

a first outlet flow line operatively coupled to the outlet and adapted to deliver a first portion of the oxygen-enriched gas to a patient;

a second outlet flow line operatively coupled to the outlet and adapted to deliver a second portion of the oxygen-enriched gas to a storage vessel; and

a valve positioned and operable to terminate the delivery of the second portion of the oxygen-enriched gas to the storage vessel responsive to an oxygen concentration of the oxygen-enriched gas being below a predetermined value, wherein the first outlet flow line remains substantially unimpeded so as to maintain the delivery of the first portion of the oxygen-enriched gas to the patient even during termination of the second portion of the oxygen-enriched gas to the storage vessel.

32. The apparatus of claim 31, wherein an oxygen concentration of the first portion of the oxygen-enriched gas is at least 80%.

33. The apparatus of claim 31, further comprising an oxygen sensor adapted to sense a concentration of oxygen-enriched gas produced by the pressure swing adsorption system, wherein the valve closes to prevent delivery of the second portion of the oxygen-enriched gas to the storage vessel responsive to the oxygen sensor sensing that the oxygen concentration of the oxygen-enriched gas is below the predetermined value.

34. The apparatus of claim 33, wherein the predetermined value is 88%.

35. The apparatus of claim 33, wherein the oxygen sensor is operatively coupled to the second outlet flow line.

36. The apparatus of claim 31, wherein the valve is positioned between the outlet of the pressure swing adsorption system and the storage vessel.

37. The apparatus of claim 31, further comprising a third outlet flow line having (a) a first end operatively coupled to the outlet of the pressure swing adsorption system, and (b) a second end, wherein the first outlet flow line and the second outlet flow line are coupled to a second end of the third outlet flow line.

38. The apparatus of claim 31, further comprising a product storage tank adapted to receive the oxygen-enriched gas from the pressure swing adsorption system, and wherein an outlet of the product tank corresponds to the outlet of the pressure swing adsorption system.

39. The apparatus of claim 31, wherein the pressure swing adsorption system is an oxygen concentrator.

40. The apparatus of claim 31, further comprising a liquefier adapted to liquefy at least a portion the second portion of the oxygen-enriched gas, and wherein the storage vessel stores the liquefied oxygen.

41. A process for supplying oxygen-enriched gas to a patient and to a storage vessel comprising the steps of:

generating an oxygen product utilizing a pressure swing adsorption system comprising a molecular sieve bed;

directing a first portion of the oxygen product to a patient;

directing a second portion of the oxygen product to a storage vessel;

monitoring an oxygen concentration of the oxygen product; and

interrupting delivery of the second portion of the oxygen product to the storage vessel responsive to the oxygen concentration being below a predetermined value, wherein directing the first portion of the oxygen product to the patient continues while the delivery of the second portion of the oxygen product is interrupted.

42. The process of claim 41, wherein the oxygen product is an oxygen-enriched gas.

43. The process of claim 41, wherein the predetermined value is 88%.

44. The process of claim 41, further comprising:

liquefying at least a portion of the second portion of the oxygen product directed to the storage vessel; and

storing the liquefied oxygen product in the storage vessel.

45. The process of claim 41, further including the step of pressurizing the second portion of the oxygen product directed to the storage vessel to a pressure greater than the pressure of the first portion of the oxygen product directed to the patient.

46. The process of claim 41, wherein the pressure swing adsorption system is an oxygen concentrator.

47. The process of claim 41, further including the step of transferring the oxygen product from the storage vessel to a portable storage vessel.

48. An apparatus for providing oxygen-enriched gas to a patient in a home environment and an ambulatory environment comprising:

a pressure swing adsorption system comprising a molecular sieve bed adapted to generate oxygen-enriched gas;

a first outlet flow line operatively coupled to the pressure swing adsorption system to direct a first portion of the oxygen-enriched gas from the pressure swing adsorption system to a patient;

a storage vessel;

a second outlet flow line operatively coupled to the pressure swing adsorption system to direct a second portion of the oxygen-enriched gas from the pressure swing adsorption system to the storage vessel;

a compressor in fluid communication with the second outlet flow line, wherein the compressor is adapted to compress the second portion of oxygen-enriched gas prior to delivery to the storage vessel; and

a coupling operatively coupled to the storage vessel, wherein the coupling is adapted to be connected with a portable tank to enable filling of the portable tank from the storage vessel.

49. The apparatus of claim 48, further comprising a liquefier adapted to liquefy at least a portion of the second portion of the oxygen-enriched gas directed to the storage vessel, and wherein the storage vessel stores the liquefied oxygen.

50. That apparatus of claim 48, wherein the pressure swing adsorption system is an oxygen concentrator.

51. A process for supplying oxygen-enriched gas to a patient and to a portable storage container comprising the steps of:

generating an oxygen product utilizing a pressure swing adsorption system comprising a molecular sieve bed;

directing a first portion of the oxygen product to a patient;

directing a second portion of the oxygen product to a storage vessel; and

filling a portable storage container with a content of the storage vessel.

52. The process of claim 51, wherein the oxygen product is an oxygen-enriched gas.

53. The process of claim 51, further comprising:

liquefying at least a portion the second portion of the oxygen product directed to the storage vessel; and

storing the liquefied oxygen product in the storage vessel, and wherein filling the portable storage container includes providing the liquefied oxygen product as the content from the storage vessel to the portable storage container.

54. The process of claim 51, wherein the pressure swing adsorption system is an oxygen concentrator.

55. The process of claim 51, wherein the first portion of oxygen product is delivered simultaneously to the patient while the second portion of oxygen product is directed to the storage vessel.

56. The process of claim 55, wherein the flow of the second portion of oxygen product is terminated if the oxygen product is measured to be below a predetermined concentration level.

57. The process of claim 56, wherein the predetermined concentration level is 88%.

58. An apparatus for filling a portable tank with an oxygen product, comprising:

a pressure swing adsorption system comprising a molecular sieve bed adapted to generate oxygen-enriched gas;

a storage vessel;

an outlet flow line operatively coupled to the pressure swing adsorption system to direct at least a portion of the oxygen-enriched gas from the pressure swing adsorption system to the storage vessel;

a compressor to receive the oxygen-enriched gas from the pressure swing adsorption system from the outlet flow line, wherein the compressor is adapted to compress the portion of the oxygen-enriched gas prior to delivery to the storage vessel; and

a coupling operatively coupled to the storage vessel, wherein the coupling is adapted to be connected with a portable tank suitable for human transport to enable filling of the portable tank with a content from the storage vessel.

59. The apparatus of claim 58, further comprising a liquefier adapted to liquefy at least a portion the oxygen-enriched gas directed to the storage vessel, and wherein the storage vessel stores the liquefied oxygen.

60. The apparatus of claim 58, wherein the pressure swing adsorption system is an oxygen concentrator.

61. A method of filling a portable tank for portable transport by a patient with an oxygen product, the method comprising the steps of:

generating an oxygen product gas utilizing a pressure swing adsorption system comprising a molecular sieve bed which receives the ambient air as an input and provides an output of the oxygen product gas at a first pressure;

pressurizing the oxygen product gas to a second pressure subsequent to the generation, the second pressure being greater than the first pressure;

directing the oxygen product at the second pressure to a storage vessel; and

filling a portable tank of sufficient size for portability by a patient with a content of the storage vessel.

62. The method of claim 61, further comprising:

liquefying at least a portion the oxygen product after the compressing step; and

storing the liquefied oxygen product in the storage vessel, and wherein filing the portable tank includes providing the liquefied oxygen product as the content from the storage vessel to the portable tank.

63. The method of claim 61, wherein the pressure swing adsorption system is an oxygen concentrator.

64. The method of claim 61 further including monitoring a purity of the oxygen product and terminating the direction of oxygen product to the storage vessel responsive to the purity being below a predetermined level.

65. A method of producing and storing liquid oxygen in an oxygen patient'"'"'s residence, comprising:

providing a liquid oxygen producing apparatus;

placing the liquid oxygen producing apparatus in a location at which a user of liquid oxygen resides;

producing liquid oxygen at the location utilizing a pressure swing adsorption system comprising a molecular sieve bed which receives the ambient air as an input and provides an output of oxygen-enriched gas; and

delivering oxygen-enriched gas produced by the pressure swing adsorption system to a patient.

66. The method of claim 65, further including monitoring a purity of the oxygen-enriched gas to determine whether a level of purity is suitable for human consumption.

67. The method of claim 65, wherein the delivering step is conducted while the liquid oxygen producing apparatus is producing the liquid oxygen.

68. The method of claim 65, wherein producing the liquid oxygen is terminated responsive to an oxygen concentration level of the oxygen-enriched gas produced by the pressure swing adsorption system being below a predetermined level.

69. The method of claim 65, further comprising storing the liquid oxygen in a dewar and transferring the liquid oxygen from the dewar to a portable storage device.

70. A home liquid oxygen ambulatory system for supplying an ambulatory portable supply of oxygen comprising:

a pressure swing adsorption system comprising a molecular sieve bed adapted to separate oxygen from ambient air for human consumption;

a liquefier adapted to receive oxygen from the pressure swing adsorption system and liquefying the oxygen;

a first storage dewar in fluid communication with the liquefier and adapted to store oxygen liquefied by the liquefier;

a second portable storage dewar adapted to store a quantity of oxygen suitable for ambulatory moveable oxygen treatment;

a monitor for measuring an oxygen concentration of oxygen from the pressure swing adsorption system; and

a controller receiving signals from the monitor, and adapted to terminate the liquefying of the oxygen responsive to the oxygen concentration being below a predetermined level.

71. The apparatus of claim 70, wherein the predetermined level of oxygen concentration is at least 88% oxygen purity.

72. The apparatus of claim 70, further including a pressure inducer adapted to increase the pressure within the first dewar for facilitating in the transfer of liquid oxygen from the first dewar to the second portable dewar.

73. The apparatus of claim 70, further comprising a flow line from the pressure swing adsorption system to a person so as to deliver oxygen from the pressure swing adsorption system to a patient simultaneous to the delivery of oxygen to the liquefier.

74. The apparatus of claim 70 including a valve operationally controlled by the controller, wherein the valve terminates the flow of oxygen to the liquefier responsive to the oxygen concentration being below a predetermined level.

75. A method for generating liquid oxygen in a home comprising:

generating a gaseous supply of oxygen for human consumption using a pressure swing adsorption system comprising a molecular sieve bed which receives the ambient air as an input and provides an output of the gaseous supply of oxygen;

monitoring a purity of the gaseous oxygen supply to determine if the level of purity is suitable for human consumption;

liquefying the gaseous supply of oxygen responsive to the level of purity being above a predetermined level;

storing the liquid oxygen in a first storage dewar;

transferring the liquid oxygen in the first storage dewar to a portable second storage.

76. The method of claim 75, wherein at least a portion of the gaseous supply of oxygen from the pressure swing adsorption system is delivered to a person for consumption.