A cooling unit comprising: an interior space; a door separating the interior space from air external to the cooling unit, wherein the door comprises a transparent window; an air curtain system having an air egress and an air-recovery ingress, wherein the air curtain system produces an air curtain between the air egress and the air-recovery ingress, the air curtain being within the interior space and spaced from the door; and an air curtain guide for guiding flow of air within the air curtain, wherein the air curtain guide is within the interior space. A method of reducing condensation on a transparent window in a door of a cooling unit is also provided.