SENSIndoor aims at the development of novel nanotechnology based intelligent sensor systems for selective monitoring of Volatile Organic Compounds (VOC) for demand controlled ventilation in indoor environments. Greatly reduced energy consumption without adverse health effects caused by the Sick Building Syndrome requires optimized ventilation schemes adapted to specific application scenarios like offices, hospitals, schools, nurseries or private homes. These must be based on selective detection and reliable quantification of relevant VOCs such as formaldehyde or benzene at ppb or even sub-ppb levels in complex environments. Priority scenarios and corresponding target gases and concentrations will be defined together with an advisory board representing health standard experts and major industrial stakeholders. The project addresses two sensor technologies with MEMS-based metal oxide semiconductor gas sensors and SiC-based gas sensitive field effect transistors. Gas sensitive layers for both sensor technologies are realized by Pulsed Laser Deposition for well-defined, stable and highly sensitive nanostructured layers. These are combined with gas pre-concentration to boost the sensitivity of the overall system. Dynamic operation of the gas sensor elements by temperature cycling combined with pattern recognition techniques is employed to further boost sensitivity and selectivity and expanded to optimally use the gas preconcentration. The project thus combines physical and chemical nanotechnologies for extremely sensitive and selective gas sensing, MEMS technologies for low-power operation as well as low-cost manufacture and finally dynamic operating modes together with advanced signal processing for unrivalled system performance. Sensor elements and systems are evaluated under controlled lab conditions derived from priority application scenarios. The final demonstration of the SENSIndoor technology will include field tests with sensor systems integrated into building control systems.