An in-line gravity filtration device for biological fluids such as blood or blood products is disclosed. The device includes a series of channels formed downstream of filtration elements. The channels are defined in cross sectional area by the distance between the filtration elements and their bottoms. The channels are configured to form flow paths to an outlet port so that air within the channels is forced downstream through the outlet port thereby minimizing air being trapped on the downstream side of the device. For optimum performance, the cross section area of a single continuous channel, or the sum of the cross sectional area of parallel channels, leading to a single outlet port, should not exceed the cross sectional area of the outlet port.