Which of the following is the most commonly used inerting gas?

• A. Nitrogen
• B. Oxygen
• C. Argon
• D. Helium

Answer: (A)

Inerting gas selection hinges on finding a gas that is non-reactive, won't support combustion, and can be supplied in bulk at low cost and easy access. Nitrogen fits best because it makes up most of the air (about 78%), so it’s readily available and inexpensive to use for large-scale blanketing or purging. It effectively displaces oxygen without introducing new hazards and remains chemically inert under typical process conditions, which helps keep ignition risks down. While argon and helium are also inert, their higher cost and limited supply make them impractical for routine, large-volume inerting. Oxygen, by contrast, would increase the oxidizer present and actually raise the risk of ignition, so it’s not used for inerting.