In one example, a build material recovery system for additive manufacturing includes: a receiving station to receive a portable container containing a build material; a separator to remove build material from a stream of air; a first conduit to carry build material in the stream of air from the receiving station to the separator; a source of negative air pressure to pull the stream of air with the build material through the first conduit from the receiving station to the separator; a humidifier to add moisture to the stream of air; and a second conduit to carry build material from the separator to the receiving station.