Carrier gas is an inert gas used to carry samples. Helium $\mathrm{(He)}$, nitrogen $\mathrm{(N_2)}$, hydrogen $\mathrm{(H_2)}$, and argon $\mathrm{(Ar)}$ are often used. Helium and nitrogen are most commonly used and the use of helium is desirable when using a capillary column.