True or False: Oxygen can be used to check for leaks in a refrigerant system provided all refrigerant has been recovered.

Using oxygen to check for leaks in a refrigerant system is not safe and is not an accepted practice within the HVAC industry. Refrigerant systems are designed to be sealed and operate under specific pressures, and introducing oxygen can create serious safety risks, including combustion, especially since many refrigerants are flammable or can form dangerous mixtures when combined with oxygen.

Checking for leaks is typically done using specialized tools and methods, like electronic leak detectors or ultraviolet dye, which do not pose the same risks. These methods effectively identify leaks without introducing oxygen or any other potentially harmful substances into the system.

Therefore, it's important to adhere to established safety protocols and utilize the recommended methods for leak detection. This ensures not only the integrity of the refrigerant system but also the safety of the technician and the environment.