What should be used to inert an integral fuel tank before repairs?

Using an inert gas, such as CO2, to inert an integral fuel tank before repairs is crucial for safety reasons. Inerting the tank reduces the risk of fire or explosion during maintenance by displacing flammable vapors. In this context, carbon dioxide (CO2) serves to lower the oxygen concentration within the tank, making combustion significantly less likely.

Inert gases, like CO2 and nitrogen, are effective because they are not reactive with the fuel or tank materials and can safely fill the void spaces in the tank. This process is typically part of a standard safety protocol before any maintenance work in fuel systems, ensuring that the environment inside the tank is as safe as possible for workers.

While other substances such as water or steam may pose problems, they can lead to corrosion, contamination, or other unintended reactions within the tank, making them unsuitable for this specific purpose. Nitrogen may also be utilized as an inerting gas, but carbon dioxide is specifically noted for its effectiveness in certain conditions, contributing to its selection as the correct answer.