Abstract: A defoaming device for separating foam and bubbles from a liquid, such as blood, is disclosed. The device can be used in conjunction with a medical device, such as a membrane oxygenator, for separating air from blood while minimizing blood contact with the antifoam agent used in the device. The device includes a reservoir and a filtering material that does not contain any antifoaming agent. This filtering material is positioned in a lower portion of the reservoir to separate foam and bubbles from the liquid. An element containing an antifoaming agent is positioned in the reservoir above the maximum surface fluid level therein and receives the foam and bubbles that rise from the filtering material. Contact of the liquid with the antifoaming agent is substantially avoided.