the art is positioned to move product e g foodstuffs from the bath toward a discharge 22 in section 10 discharge 22 is adapted to discharge product onto a spiral conveyor 24 contained inside a second section 26 which is a spiral type mechanically refrigerated freezer mechanical spiral type refrigerators such as 26 are well known in the art and comprise a refrigerated housing 28 a product inlet 30 at a low level and a product discharge 32 at a higher level the product to be frozen moves from the inlet 30 around the spiral and is discharged out of the discharge opening 32 the interior of the housing 28 is cooled to freezing temperatures by means of a mechanical refrigeration system not shown as is well known in the art sections 10 and 26 are mated or married together in a gas tight relationship so that cryogen vaporizing inside of the immersion freezer 10 will flow out of the discharge 22 and into the housing 28 of mechanical refrigerator 26 movement of the vaporized cryogen is effected by a cryogen mover 36 which can be an exhaust fan the exhaust fan is so constructed that equal volumes of cryogen are admitted through the gas inlet 49 of freezer 26 and discharged from outlet 32 of freezer 26 flow of vaporized cryogen is as shown by arrows 50 the exhaust fan includes a bypass system.