Oil and grease should NEVER be used on a regulator for which gas?

The correct choice is based on the fact that oil and grease pose a significant risk when used with oxygen. Oxygen is a highly reactive gas, and under certain conditions, even small amounts of oil or grease can ignite and cause explosive reactions. This risk is particularly high in environments where oxygen is under pressure, such as in gas regulators and cylinders. The presence of oil or grease can lead to spontaneous combustion when it comes into contact with concentrated oxygen, which is why it's critical to avoid any lubricant with oxygen equipment.

In contrast, nitrogen, argon, and helium are inert gases and do not react chemically with oils or greases in the same dangerous manner. Therefore, they do not present the same level of risk associated with lubrication in their delivery systems, making it safe to use oils and greases with them as needed. Understanding the dangers of handling oxygen in conjunction with combustible materials is vital for ensuring safety in HVAC and related applications.