The purpose of this paper is to address the problem of maintaining coherent perceptual information in a mobile robotic system working over extended periods of time, interacting with a user and using multiple sensing modalities to gather information about the environment and specific objects. We present a system which is able to use spatial and olfactory sensors to patrol a corridor and execute user requested tasks. To cope with perceptual maintenance we present an extension of the anchoring framework capable of maintaining the correspondence between sensor data and the symbolic descriptions referring to objects. It is also capable of tracking and acquiring information from observations derived from sensor-data as well as information from a priori symbolic concepts. The general system is described and an experimental validation on a mobile robot is presented.