This paper describes the AdvancedTCA (ATCA) Shelf requirements to cool all the Boards and facilitate the interoperability of Shelf slots. It also covers the flow impedance issues of Boards and introduces a methodology of impedance balancing. Further, to date, there is no standard measurement technique that can be adopted to compare shelves in terms of air flow volume through each slot in the Shelf. This paper describes a methodology of evaluating airflow volumes through each slot in an ATCA Shelf that can be used to benchmark each Shelf. The recent designs that populate the Board with mezzanine cards (AMCs) demand air flow at a higher flow impedance. The cooling challenges posed by the introduction of AMCs on a Board are enunciated as well.