The chapter discusses different detectors used in gas chromatography, which are essential for providing information in a usable format for analysis. The gas density balance (GDB) is a detector whose response can be calculated from physical properties and remains consistent. The thermal conductivity detector (TCD) is universal and widely used, while the flame ionization detector (FID) is popular for its reliability in detecting organic vapors. The thermo ionic detector (TID) and flame photometric detector (FPD) are selective detectors for specific compounds.