National Refrigerants service gases Oxygen Free Nitrogen (OFN) and Tracer Gas are used for pressure testing and leak detecting before introducing expensive refrigerants into the system.
When a new system is installed or an existing system is repaired the refrigerant circuit may no longer be airtight leading to loss of refrigerant.

Pressure testing should always be performed when a refrigerant circuit is broken to ensure that these F-Gases do not escape into the atmosphere.

Normally this is done using nitrogen which is the most cost-effective inert gas and makes up 78% of the air we breathe.

For critical systems, tests should be performed using Tracer Gas which is 95% nitrogen and 5% hydrogen, as hydrogen has the smallest known molecule it will find the smallest leak in any system.