We have developed a Multi-Layered Hollow Fiber Membrane, MHF which has a unique structure and good gas permeability. The thin intermediate layer of the MHF is of non-porous structure and permeable to gas and impermeable to liquid. The outside and inside support layers of the MHF are made of polyolefin with a porous structure which has a porosity of about 40vol%. This membrane is useful for artificial lung and also deaerator to remove dissolved gas in the semiconductor pure water, developer and industrial alcohol.
