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Cryogenic Freezer. A freezer, usually consisting of an insulated tunnel in which liquid nitrogen (q.v.) with a boiling point (q.v.) of -320¦F (-195.6¦ C) or liquid carbon dioxide (q.v.) with a boiling point of -109¦F (-78¦C) are the freezing media. Product freezing is normally carried out in three stages, namely, pre-cooling with cold gas, actual freezing by spraying the liquefied gases on the product, and tempering to the desired exit temperature, again with cold gas. In the case of liquid carbon dioxide, freezing is effected by the dry ice snow into which the liquid converts when its storage pressure is released.