What refrigerant can be used as a trace gas when checking for leaks?

A common refrigerant used as a trace gas for leak detection is helium. Its small atomic size allows it to escape through tiny leaks, making it highly effective for identifying areas of concern. Additionally, helium is non-toxic and environmentally friendly, which adds to its appeal for leak detection applications. Other refrigerants, like refrigerant R-134a, can also be used, but helium is often preferred for its sensitivity and safety.