Patent ID: 8343347

Claim:
A dual stage filtration apparatus comprising: a cartridge housing having a first filtration stage including first semi-permeable filtering elements and a second filtration stage including second semi-permeable filtering elements and a fluid inlet port for receiving raw unfiltered fluid and a fluid outlet port for discharging purified fluid after it has passed through the first and second filtration stages, wherein the apparatus has an intrastage space that receives fluid that has been filtered in the first filtration stage prior to being filtered again in the second filtration stage, the fluid inlet port being in fluid communication only with the first filtration stage, while the fluid outlet port is in fluid communication only with the second filtration stage, and a feature that permits visual inspection of at least a portion of the second semi-permeable filtering elements to detect whether a breach has occurred in the first filtration stage, wherein the feature comprises a label that is attached to an outer surface of the cartridge housing so as to cover and obscure a portion of the second semi-permeable filtering elements and includes a first cutout formed therein, the label being disposed over the portion of the second semi-permeable filtering elements such that the second semi-permeable filtering elements are visible through the first cutout; wherein the cartridge housing is only open to the exterior at the fluid inlet port and the fluid outlet port which are located at the same end of the cartridge housing; wherein the first and second semi-permeable filtering elements are hollow fiber semi-permeable filtering elements, the first semi-permeable filtering elements comprising a center bundle of hollow fibers and the second semi-permeable filtering elements comprising an outer bundle of hollow fibers that surround the center bundle such that the second semi-permeable filtering elements are disposed adjacent the cartridge housing and are visible therethrough.