A closed system suitable for the aseptic culture of therapeutic cells comprising: (i) a vessel comprising: a gas permeable portion suitable for supporting cell growth and allowing delivery of gases to the cells during culturing, and at least one wall adjoined to a base, wherein said vessel defines an internal volume for containing a requisite volume of medium to support a cell culture, (ii) a vent comprising a conduit defining an interior orifice and an exterior orifice distal therefrom in fluid communication with each other which allows balancing of pressure during filling the vessel by allowing gases to exit and during the cell-emptying process allows gases to enter the interior volume, wherein the conduit extends from the exterior of the closed system through a structural feature of the vessel and extends into the internal volume of the vessel and terminates therein with the interior orifice, and wherein the interior orifice is arranged not to contact the medium in the vessel or wherein the interior orifice is covered with a liquid impermeable membrane or a liquid non-return valve, such that exposure of the internal orifice to liquid is minimised and therefore the interior orifice is not susceptible to blockage by liquid during filling and emptying of liquid medium, and wherein the exterior orifice is capable of attaching to a sterile filter, (iii) a port or ports for aseptic introduction of fluids and cells into the vessel, a port or ports for fluids to exit the system without exposing the system to the external environment which allows cells grown therein to exit the system under gravity when the system is orientated to put the cells in fluid communication with the exit port. (i) a vessel comprising: a gas permeable portion suitable for supporting cell growth and allowing delivery of gases to the cells during culturing, and at least one wall adjoined to a base, wherein said vessel defines an internal volume for containing a requisite volume of medium to support a cell culture, a gas permeable portion suitable for supporting cell growth and allowing delivery of gases to the cells during culturing, and at least one wall adjoined to a base, wherein said vessel defines an internal volume for containing a requisite volume of medium to support a cell culture, (ii) a vent comprising a conduit defining an interior orifice and an exterior orifice distal therefrom in fluid communication with each other which allows balancing of pressure during filling the vessel by allowing gases to exit and during the cell-emptying process allows gases to enter the interior volume, wherein the conduit extends from the exterior of the closed system through a structural feature of the vessel and extends into the internal volume of the vessel and terminates therein with the interior orifice, and wherein the interior orifice is arranged not to contact the medium in the vessel or wherein the interior orifice is covered with a liquid impermeable membrane or a liquid non-return valve, such that exposure of the internal orifice to liquid is minimised and therefore the interior orifice is not susceptible to blockage by liquid during filling and emptying of liquid medium, and wherein the exterior orifice is capable of attaching to a sterile filter, (iii) a port or ports for aseptic introduction of fluids and cells into the vessel, a port or ports for fluids to exit the system without exposing the system to the external environment which allows cells grown therein to exit the system under gravity when the system is orientated to put the cells in fluid communication with the exit port.