To Use the Electronic Leak Detector, the System Must Contain

Multiple Choice

To use the electronic leak detector, the system must contain at least some refrigerant. If the system is operating with a small leak, plenty of pressurized refrigerant is left in the system. But if the system is void of refrigerant, it must first be pressurized with __________, to which a trace of refrigerant has been added.

A) halogen
B) hydrogen
C) nitrogen
D) oxygen