The invention provides a fluid filtration apparatus which includes at least a functional biomedical device having an inlet and an outlet, a first biological fluid container in fluid communication with the inlet of said functional biomedical device, a first biological fluid receiving container downstream of the functional biomedical device in fluid communication with the outlet of the functional biomedical device, and having an excess of fluid, such as air or gas, in the first biological fluid container or biological fluid receiving container (either placed therein during manufacture, or addedlater) sufficient to drain the system. A method of using the apparatus is disclosed.