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.