An aisle containment system (40, 340) comprising: a plurality of cabinets (46, 160, 162) having a front, a back, sides, a bottom and a top, wherein the cabinets (46, 160, 162) are arranged in a first row and a second row across from the first row defining an aisle therebetween; a ceiling structure secured to a front edge of the top of each cabinet (46, 160, 162), and a door assembly (48, 200, 500) secured to the end of a cabinet (46, 160, 162) in the first row and the end of a cabinet (46, 160, 162) in the second row, wherein the door assembly (48, 200, 500) extends across the aisle, wherein the ceiling structure includes a plurality of vertical panels (50, 62, 121, 350, 360), each vertical panel having a top flange (56, 72, 356) and a bottom flange (66, 362), the bottom flange secured to one of the cabinets (46, 160, 162) and the top flange having a plurality of slots that extend a length of the vertical panel, whereby the slots are positioned to enable opposing cabinets (46, 160, 162) to have different widths; wherein the door assembly (48, 200, 500) includes a frame (208, 508) secured to the sides of the cabinets (46, 160, 162) at the end of the aisle, a transom secured to the ceiling structure at the end of the aisle and doors secured to the frame for sealing the end of the aisle; and wherein the transom (220, 520) includes a top, bottom and sides, the sides of the transom include horizontal slots (226,526) for receiving fasteners to mount the transom to a vertical panel secured to the cabinets (46, 160, 162), whereby the horizontal slots (226,526) enable the transom to be adjusted to vary the width of the aisle. a plurality of cabinets (46, 160, 162) having a front, a back, sides, a bottom and a top, wherein the cabinets (46, 160, 162) are arranged in a first row and a second row across from the first row defining an aisle therebetween; a ceiling structure secured to a front edge of the top of each cabinet (46, 160, 162), and a door assembly (48, 200, 500) secured to the end of a cabinet (46, 160, 162) in the first row and the end of a cabinet (46, 160, 162) in the second row, wherein the door assembly (48, 200, 500) extends across the aisle, wherein the ceiling structure includes a plurality of vertical panels (50, 62, 121, 350, 360), each vertical panel having a top flange (56, 72, 356) and a bottom flange (66, 362), the bottom flange secured to one of the cabinets (46, 160, 162) and the top flange having a plurality of slots that extend a length of the vertical panel, whereby the slots are positioned to enable opposing cabinets (46, 160, 162) to have different widths; wherein the door assembly (48, 200, 500) includes a frame (208, 508) secured to the sides of the cabinets (46, 160, 162) at the end of the aisle, a transom secured to the ceiling structure at the end of the aisle and doors secured to the frame for sealing the end of the aisle; and wherein the transom (220, 520) includes a top, bottom and sides, the sides of the transom include horizontal slots (226,526) for receiving fasteners to mount the transom to a vertical panel secured to the cabinets (46, 160, 162), whereby the horizontal slots (226,526) enable the transom to be adjusted to vary the width of the aisle.