Redundant filtration system that includes at least one barrier filter as a process filter, the barrier filter having both hydrophilic and hydrophobic paths, allowing both fluid and gas permeability. The need for vents is eliminated, as is an intermediate drain filter. The device also can be dried in series. The filtration system includes a network of conduits and receptacles, the network receiving liquid raw and/or starting material at one end, conducting it through the process stream defined thereby, and producing the desired liquid product at another end. The network is provided with one or more in-puts for introducing liquid raw material into the fluid process stream, and one or more output ports for discharging fluid out of the fluid process stream. The network is preferably an essentially closed network, and also, preferably sterile and/or aseptic.
