Abstract: A louver damper device for the control of fluid flow within a conduit. The louver damper device includes one or more louvers, wherein each louver is a single-walled pivotable unit. The ends of louvers that are adjacent to one another are designed with coupling legs so that when the device is actuated into a blocking position within the conduit, the louver ends become sealingly engaged so as to form relatively small sealing chambers therebetween. Purge air may then be delivered to the sealing chambers to ensure a complete blocking of fluid movement within the conduit. The louvers adjacent to the conduit walls include end modifications similar to those provided to the intermediate louvers. Alternatively, flexible sealing hubs may be affixed to the conduit walls for engagement with modified ends of those perimeter louvers designed to sweep away any particulate residing on the flexible hubs without affect on the seal between those louvers and the interior conduit walls.