Which gas is used for purging an aircraft fuel tank?

The use of nitrogen for purging an aircraft fuel tank is essential due to its inert properties. Nitrogen is a non-reactive gas that helps to displace flammable vapors and reduces the risk of combustion or explosion during fuel tank maintenance or repair. By purging the tank with nitrogen, the oxygen concentration is minimized, which is crucial for ensuring a safe working environment.

Other gases like carbon monoxide are hazardous and toxic, making them inappropriate for this purpose. While carbon dioxide can sometimes be used in certain situations, it is less ideal than nitrogen because it can still contribute to some combustion risks under certain conditions. Helium and argon, while inert, are generally not utilized for this application primarily due to their cost and availability. Therefore, nitrogen stands out as the safest and most effective choice for purging an aircraft fuel tank.