The TCD is one of the more widely used detectors for gas chromatography because it is simple in construction, rugged, versatile, sensitive, relatively linear over a wide range, nondestructive to the sample, and inexpensive. It is because of these qualities that it continues to be widely used.

The TCD consists of a block (usually metallic) containing a cavity through which the gas flows. A heated element (resistance wire or thermistor) is positioned in the flow path of the gas. For practical considerations a differential method is usually used that requires two cavities and two heated elements. only carrier gas passes through one cavity and the column effluent through the other. For process analysis, a reference and sample gas are used.
Precise matching of filaments and thermistors over an extended current-resistance curve and under controlled heat dissipation conditions ensure superior detector performance
Rigid gas and electrical leakage tests and are run on specified zero gas
Micro-cells and GADEs are tested for signal output
Flow-through, semi-diffusion and diffusion geometries
Detector Sensitivity: Depends on several factors. Most basic is the difference in thermal conductivity (or other characteristics) between the background (carrier, reference) gas and the sample.
Sensitivity of hot wire thermal conductivity detectors (TCD) depends on the internal geometry, type of detector elements, and the temperature differential (Dt) between filaments and cell block.
Thermistor detectors are at their best in sub-ambient and ambient operation.
Gas density detectors (GADE) vary in sensitivity directly with the difference in molecular weight, as well as with the number and type of sensor elements