In a refrigeration system, which gases are considered non-condensables?

• A. Oxygen and Argon
• B. Air and Nitrogen
• C. Carbon Dioxide and Helium
• D. Hydrogen and Neon

Answer: (B)

Non-condensables are gases that do not liquefy at the condenser’s operating temperature and pressure, so they stay in the gas phase inside the system. They usually enter from leaks and are mainly the air that gets into the refrigerant circuit. Since air is mostly nitrogen, nitrogen is the typical non-condensable you’ll encounter in a refrigeration system. Nitrogen remains a gas while the refrigerant condenses, which raises condenser pressure and reduces heat-transfer efficiency. That’s why “Air and Nitrogen” is the best answer: it points to the common source (air leaks) and the representative non-condensable gas (nitrogen). Other gases like oxygen, argon, helium, or neon can be present in trace amounts, but the standard HVAC context emphasizes air and its nitrogen component as the typical non-condensables.