Hot/cold aisle is a format for racks of servers and generally IT apparatus inside a data center where the rack fronts face the rack fronts of the adjacent row. When cold aisle containment approach is used, row doors, aisle ceilings or overhead vertical walls are installed to contain the cold air coming from the cooling systems into the cold aisles. As the opposite, in hot aisle containment the hot air is contained so that the CRAC units just receive hot air.