The advancement in chemi-resistive gas sensing at room temperature employ chalcogenides as an active layer owing to their excellent physicochemical characteristics such as lacking of the oxygen in the crystal lattice and low bandgap energy. Herein, we report the preparation of chalcogenide (Sn20Te80) using heat treatment and their usage as active layer in the chemi-resistive sensor for the detection of most prominent toxic gas analytes such as NO2 and NO under room temperature (~25 0C) measurement. The electron interaction after the exposure of analytes and determination of their trapping at charged centres affirms the sensing characteristics with excellent recovery and response time. The higher order of concentrations (NO2 and NO) resulted in increased sensitivity with maximum exposure limit of 5ppm (NOx) as per OSHA standards. The mechanism of chalcogenide (Sn20Te80) based sensor device deposited over IDE is tested to the exposure of NO2 and NO gas and the sensor response with sensitivity and selectivity is discussed.