NILU has published a report on specifications for air quality monitoring sensor systems. This report explains technical terms related to measuring performances, as well as providing recommendations and requirements in connection with preparation of tenders. The report goes through existing instrumentation for air quality measurement in Norway and current legislation on the subject. It mentions possible applications for new measurement technologies. An overview of metrological terms with explanations gives the reader basic knowledge necessary to interpret instrument specifications. The report identifies some important parameters related to the quality of sensor systems.