A data cabinet comprising: a cabinet body for enclosing one or more rack-mounted units, the cabinet body comprising an inlet for allowing a cooling medium to enter the cabinet and an outlet for allowing the cooling medium to exit the cabinet, wherein the outlet is configured to be connected to an outlet manifold for carrying the cooling medium away from the data cabinet; a rack for supporting the one or more rack-mounted units within the cabinet body, the rack and the cabinet body being configured to define a first plenum space in fluid communication with the inlet and a second plenum space in fluid communication with the outlet; and one or more sealing members (161, 162) configured to substantially block the cooling medium from flowing between the first and second plenum spaces via the rack, whilst permitting the cooling medium to flow from the first plenum space to the second plenum space through the one or more rack-mounted units, characterised in that the data cabinet further comprises: an aperture (191, 192) configured to allow one or more cables to pass through a wall of the cabinet body; a cable seal capable of conforming to the shape of one or more cables passing through the aperture, so as to restrict fluid flow through the aperture; an opening for permitting access to an interior of the cabinet body; a door (170, 180) for closing said opening; and a door seal (171, 181; 471) configured to form a substantially gastight seal around the door when closed; wherein the one or more sealing members, the cable seal and the door seal are each configured to form an anechoic and hermetic seal, such that the data cabinet is anechoically and hermetically sealed from a surrounding environment. a cabinet body for enclosing one or more rack-mounted units, the cabinet body comprising an inlet for allowing a cooling medium to enter the cabinet and an outlet for allowing the cooling medium to exit the cabinet, wherein the outlet is configured to be connected to an outlet manifold for carrying the cooling medium away from the data cabinet; a rack for supporting the one or more rack-mounted units within the cabinet body, the rack and the cabinet body being configured to define a first plenum space in fluid communication with the inlet and a second plenum space in fluid communication with the outlet; and one or more sealing members (161, 162) configured to substantially block the cooling medium from flowing between the first and second plenum spaces via the rack, whilst permitting the cooling medium to flow from the first plenum space to the second plenum space through the one or more rack-mounted units, characterised in that the data cabinet further comprises: an aperture (191, 192) configured to allow one or more cables to pass through a wall of the cabinet body; a cable seal capable of conforming to the shape of one or more cables passing through the aperture, so as to restrict fluid flow through the aperture; an opening for permitting access to an interior of the cabinet body; a door (170, 180) for closing said opening; and a door seal (171, 181; 471) configured to form a substantially gastight seal around the door when closed; wherein the one or more sealing members, the cable seal and the door seal are each configured to form an anechoic and hermetic seal, such that the data cabinet is anechoically and hermetically sealed from a surrounding environment. an aperture (191, 192) configured to allow one or more cables to pass through a wall of the cabinet body; a cable seal capable of conforming to the shape of one or more cables passing through the aperture, so as to restrict fluid flow through the aperture; an opening for permitting access to an interior of the cabinet body; a door (170, 180) for closing said opening; and a door seal (171, 181; 471) configured to form a substantially gastight seal around the door when closed; wherein the one or more sealing members, the cable seal and the door seal are each configured to form an anechoic and hermetic seal, such that the data cabinet is anechoically and hermetically sealed from a surrounding environment.