Check the listing for details. FIGARO TGS813 TGS-813 Gas Sensor. Condition: New. Listed at 11.20 USD. 1 Pcs FIGARO TGS813 Gas Sensor - for the detection of Combustible Gases. In the presence of a detectable gas, the sensor's conductivity increases depending on the gas concentration in the air. A simple electrical circuit can convert the change in conductivity to an output signal which corresponds to the gas concentration.