A porous asymmetric hollow polymer fiber membrane having an inside surface having a coarse porous structure and an outside surface having a dense porous structure, the average pore size rating of the pores at the inside surface being greater than the average pore size rating of the pores at the outside surface, as well as filters and filter devices comprising one or more of the hollow fiber membranes, the filter and devices preferably being arranged to direct fluid flow from the inside surface of the membranes to the outside surface, and methods of using the filters and filter devices, are disclosed.