A freezer having an inlet, an inlet portion having at least one inlet blower, an outlet, an outlet portion having at least one outlet blower, and a conveyor configured to transport products from the inlet to the outlet of the freezer the inlet blower and the outlet blower configured to circulate gas or a gas and cryogen mixture to impinge onto products transported on the conveyor, wherein at least one of the at least one inlet blower and the at least one outlet blower is configured to be controlled independently of the other to provide no less than a neutral pressure condition at the inlet and outlet portions. A method for controlling gas flow within and minimizing air infiltration into such a freezer by controlling a speed of the inlet blower and the outlet blower independently to provide no less than a neutral pressure condition at the inlet and outlet portions.
