A freezer for a product , in particular for a food product, to be conveyed through a processing atmosphere, comprising: - a housing having an internal space with the processing atmosphere for reducing a temperature of the product , said internal space comprising an inlet ; - a cryogen delivery pipe in fluid communication with the internal space for delivering a cryogenic substance to said internal space ; - an inlet exhaust in fluid communication with the inlet to the internal space ; - an outlet exhaust in fluid communication with an outlet to the internal space ; - a main exhaust in fluid communication with the internal space ; and - a pressure balance apparatus in communication with the processing atmosphere to restrict atmosphere external to the freezer from reaching the internal space , the pressure balance apparatus comprising a blower disposed at the outlet of the internal space to direct a pressurized flow of the processing atmosphere to the internal space responsive to a first signal , characterized by - the pressure balance apparatus further comprising at least one sensor exposed to the processing atmosphere for generating the first signal indicating an amount of oxygen (O 2 ) at the internal space ; - a nozzle in fluid communication with the blower for directing the pressurized flow at the outlet , said nozzle being mounted to direct the pressurized flow toward the internal space ; and - a controller in communication with the at least one sensor and the blower , the controller arranged to receive the first signal from said at least one sensor and to generate a second signal to said blower responsive to said first signal for controlling the blower . - a housing having an internal space with the processing atmosphere for reducing a temperature of the product , said internal space comprising an inlet ; - a cryogen delivery pipe in fluid communication with the internal space for delivering a cryogenic substance to said internal space ; - an inlet exhaust in fluid communication with the inlet to the internal space ; - an outlet exhaust in fluid communication with an outlet to the internal space ; - a main exhaust in fluid communication with the internal space ; and - a pressure balance apparatus in communication with the processing atmosphere to restrict atmosphere external to the freezer from reaching the internal space , the pressure balance apparatus comprising a blower disposed at the outlet of the internal space to direct a pressurized flow of the processing atmosphere to the internal space responsive to a first signal , - the pressure balance apparatus further comprising at least one sensor exposed to the processing atmosphere for generating the first signal indicating an amount of oxygen (O 2 ) at the internal space ; - a nozzle in fluid communication with the blower for directing the pressurized flow at the outlet , said nozzle being mounted to direct the pressurized flow toward the internal space ; and - a controller in communication with the at least one sensor and the blower , the controller arranged to receive the first signal from said at least one sensor and to generate a second signal to said blower responsive to said first signal for controlling the blower . <EOS>