A build material management system for a 3D printing system is described in which a non-fused purged build material port is to output purged non-fused build material from a build material transportation system. An emptying of substantially all non-fused build material from at least a portion of the build material transportation system to the non-fused purged build material port in response to a received purge signal is controlled by processing circuitry of the build material management system.