An air containment system is configured to span an aisle defined by rows of racks. The air containment system includes a frame structure having two end frames provided at respective ends of the air containment system, and at least two horizontal beams, one for each side of the air containment system, releasably secured to the end frames. The frame structure is adjustable to achieve a desired height, length and width as required for a particular application of the air containment system. A kit providing an air containment system is further disclosed.