Which substance is prohibited for pressure testing in refrigeration systems?

Using oxygen for pressure testing in refrigeration systems is prohibited primarily due to safety concerns. Oxygen can support combustion, which raises the risk of fire or explosion in the presence of flammable materials, including oils and lubricants found in refrigeration systems. When systems are pressurized with oxygen, any spark or heat source can ignite combustible materials, resulting in dangerous situations.

In practical terms, non-flammable gases are preferred for pressure testing because they do not pose a combustion risk and can be utilized safely in various environments without the threat of ignition. Common choices like nitrogen are favored as they are inert and safe for such applications, allowing technicians to effectively check for leaks and ensure the integrity of the system without introducing hazardous elements.