PURPOSE: To allow supply of a product flow formed by stable, saturated cryogen substantially not containing pollutants by filling the cryogen as a saturated liquid in a tank to wash away the pollutants down to the bottom region of the tank.

CONSTITUTION: Cryogen is already filled in tanks 12, 14 and then a tank 16 is filled therewith. The cryogen is filled via top head space regions 18, 20, 22 to wash pollutants down to bottom regions 24, 26, 28. When the tank 16 is filled, the pollutants are washed down to a bottom region 28. The flow of a saturated liquid (having high content of pollutants) is removed out of the bottom region 26 and gasified to form a overheated vapor. The primary flow of the overheated vapor is introduced to the bottom region 24 for scrubbing the pollutants from the overheated vapor, to produce a cryogen vapor scrubbed in the top head space region 18. The flow of products substantially not containing the pollutants is removed from the top head space 18.