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A single-chip gas detection system fabricated in industrial CMOS technology combined with post-CMOS micro-machining is presented. The sensors rely on a chemo-sensitive polymer layer, which absorbs predominantly volatile organic compounds (VOCs). A mass-sensitive resonant-beam oscillator, a capacitive sensor incorporated into a second-order ΣΔ-modulator, a calorimetric sensor with low-noise signal conditioning circuitry and a temperature sensor are monolithically integrated on a single chip along with all necessary driving and signal conditioning circuitry. The preprocessed sensor signals are converted to the digital domain on chip. An additional integrated controller sets the sensor parameters and transmits the sensor values to an off-chip data recording unit via a standard serial interface. A 6-chip-array has been flip-chip packaged on a ceramic substrate, which forms part of a handheld VOC gas detection unit. Limits of detection (LOD) of 1-5 ppm n-octane, toluene or propan-1-ol have been achieved.