A data centre (10) includes one or more controllable air circulation systems (e.g. air optimiser (11)), one or more cold aisles (15) and/or one or more hot aisles (16), one or more rows of racks (14), the data centre being so arranged that in use cooling air (18) passes, under the control of the one or more controllable air circulation systems, from a cold aisle (15) through the racks (14) and/or through the racks (14) to a hot aisle (16). An access door (20), which provides access to at least one of the aisles, is movable between an open position allowing personnel access to the aisle and a closed position. The door (20) has an aperture (25) in which is provided a controllable air intake arrangement, for example comprising a vent (17) in the form of multiple vertically extending rotatable blades (28). The width (24) of the door is wider than the width (26) of the aisle associated with the door (20), so that the width of the aperture (25) may be larger than or substantially equal to the width (26) of the aisle. Air-flow into the aisle may therefore be subjected to less of a constriction than if the door (20) and aperture (25) were narrower.