The indoor air quality detector is a simple, low-cost and low-maintenance VOC transmitter based on modern bio-semi-conductor technology. The transmitter detects the VOC content in air and emits a proportional, linear, analog 0-10 V or digital RS 485/ModBus signal. In case of restart/voltage breakdown a signal output is set to 100 % for 20 minutes of maximum ventilation. During this time the IAQ-Gard adopts the current VOC value as 450 ppm basic value (CO2 equivalent). Due to the thereby output signal of 1,125V there is a basic ventilation (basic value) of approx. 11 %. In case of improvement of the air quality an automatic correction of the basic value is effected. The normal CO2 values are not causing any problems in closed areas but different substances like VOC can be responsible for symptoms like eye irritations, headaches, feebleness, dizziness, as well as diseases and accordingly overexertion like sick-building –syndrome. Beyond measurement of CO2 concentration the IAQ Transmitter detects the air quality similar to human sensation. That’s why VOC measurement is the perfect method to define air quality. Additionally the IAQ-Gard is suitable for almost all application areas. Furthermore there are a lot of integrated options for measurement and regulation of the temperature.