An air separation method comprising: conducting a cryogenic rectification process that comprises distilling compressed and purified air, formed by compressing the air and then purifying the air within a purification unit, the compressed and purified air is cooled in a main heat exchanger and distilled into at least a nitrogen-rich fraction and an oxygen-rich fraction within a distillation column unit having at least a higher pressure column and a lower pressure column, the lower pressure column being operatively associated with the higher pressure column in a heat transfer relationship and connected to the higher pressure column such that a crude liquid oxygen column bottoms produced in the higher pressure column is introduced into and further refined in the lower pressure column; and the cryogenic rectification process being conducted such that a first liquid stream and a second liquid air stream are produced that contain oxygen and nitrogen, the first liquid stream composed of the crude liquid oxygen column bottoms from the higher pressure column and the second liquid air stream having a lower oxygen content than the first liquid stream; and an argon content no less than the compressed and purified air after purification in the purification unit; characterized by the method further comprising: subcooling the second liquid air stream through indirect heat exchange with the first liquid stream in a dedicated heat exchanger (116, 156) distinct from the main heat exchanger; and introducing the subcooled second liquid air stream into the lower pressure column at a column location above that at which the crude liquid oxygen column bottoms or any portion thereof is introduced into the lower pressure column to increase a liquid to vapor ratio within the lower pressure column below the column location into which the subcooled second liquid air stream is introduced and to increase oxygen recovery of the distillation column unit. conducting a cryogenic rectification process that comprises distilling compressed and purified air, formed by compressing the air and then purifying the air within a purification unit, the compressed and purified air is cooled in a main heat exchanger and distilled into at least a nitrogen-rich fraction and an oxygen-rich fraction within a distillation column unit having at least a higher pressure column and a lower pressure column, the lower pressure column being operatively associated with the higher pressure column in a heat transfer relationship and connected to the higher pressure column such that a crude liquid oxygen column bottoms produced in the higher pressure column is introduced into and further refined in the lower pressure column; and the cryogenic rectification process being conducted such that a first liquid stream and a second liquid air stream are produced that contain oxygen and nitrogen, the first liquid stream composed of the crude liquid oxygen column bottoms from the higher pressure column and the second liquid air stream having a lower oxygen content than the first liquid stream; and an argon content no less than the compressed and purified air after purification in the purification unit; characterized by the method further comprising: subcooling the second liquid air stream through indirect heat exchange with the first liquid stream in a dedicated heat exchanger (116, 156) distinct from the main heat exchanger; and introducing the subcooled second liquid air stream into the lower pressure column at a column location above that at which the crude liquid oxygen column bottoms or any portion thereof is introduced into the lower pressure column to increase a liquid to vapor ratio within the lower pressure column below the column location into which the subcooled second liquid air stream is introduced and to increase oxygen recovery of the distillation column unit. subcooling the second liquid air stream through indirect heat exchange with the first liquid stream in a dedicated heat exchanger (116, 156) distinct from the main heat exchanger; and introducing the subcooled second liquid air stream into the lower pressure column at a column location above that at which the crude liquid oxygen column bottoms or any portion thereof is introduced into the lower pressure column to increase a liquid to vapor ratio within the lower pressure column below the column location into which the subcooled second liquid air stream is introduced and to increase oxygen recovery of the distillation column unit.