Gas source is the place where the carrier gas and auxiliary gas comes from. Generally the carrier gases are hydrogen, nitrogen, helium, argon and air etc.

The selction of carrier gas is based on requirements of detector, and also the effect of analytic method to analytic period, column efficiency and sensitivity. For example, from the point of column efficiency, it requires small diffusion coefficient of carrier gas. In order to obtain a good peak, commonly use nitrogen as carrier gas. For TCD, in order to improve the sensitivity, usually adopts large conductive hydrogen (helium) as carrier gas instead of nitrogen or argon. For safety and analytic period consideration, helium is better than hydrogen. However, due to few helium sources and its relatively high price, in practice, it commonly uses hydrogen as carrier gas. For FID, using nitrogen as carrier gas is safe and high sensitivity can be obtained. In conclusion, for TCD, it is better to use hydrogen or helium as carrier gas. If uses nitrogen, argon or air as carrier gas, the sensitivity will be lower, meanwhile, N type peak or W type peak will appear easily. FID and FPD usually use nitrogen as carrier gas, in some special cases, hydrogen may be also used as carrier gas. ECD often uses nitrogen as carrier gas.