🔍 Key Concepts

• Environmental phase-out of CFC (chlorofluorocarbon) refrigerants under the Montreal Protocol • Matching newer HFC (hydrofluorocarbon) refrigerants to the older refrigerants they commonly replaced • Typical uses: which older refrigerant was widely used in small refrigeration systems (like domestic refrigerators)

💭 Think About

• Think about which of the listed refrigerants (R-12, R-22, R-11, R-123) was a common older refrigerant in small refrigeration and air-conditioning units that needed an ozone-safer replacement. • Consider which ones are CFCs (fully halogenated, high ozone depletion) versus HCFCs (partially halogenated, lower ozone depletion) and how that affects what type of replacement was chosen. • Ask yourself: which older refrigerant’s operating pressures and temperatures are most similar to R‑134a, making it a practical retrofit or design replacement?

✅ Before You Answer

• Identify which option is a CFC used in older automotive and domestic refrigeration systems. • Eliminate refrigerants that are mostly associated with large chillers or low-pressure centrifugal systems, not small sealed systems. • Verify which of the listed options is most commonly mentioned together with R‑134a in discussions about phase-out and retrofits.