In the trace gas method, a trace amount of refrigerant is added to which gas?

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

Answer: (B)

The trace gas method relies on mixing a very small amount of refrigerant with a carrier gas so its presence can be detected and tracked. The carrier gas should be inert and nonreactive with the refrigerant or the system, plus be practical and inexpensive. Nitrogen fits this role well, providing a stable, inert medium that won’t react or interfere with measurements, while allowing a known trace concentration of refrigerant to be detected by the sensors. Other options are less suitable: helium and argon can be used in some leak tests but are more costly or less practical as a routine carrier for refrigerants, and oxygen would introduce reactivity and safety concerns that complicate detection.