Which refrigerant is described as an acceptable substitute for all new household refrigerators and freezers?

• A. R22
• B. Ammonia
• C. Isobutane
• D. R134a

Answer: (C)

This question tests which refrigerant is described as an acceptable substitute for all new household refrigerators and freezers. Isobutane, called R600a, is a hydrocarbon refrigerant with a very low global warming potential compared with common HFCs. Because of its environmental advantages and strong efficiency in small, sealed appliance systems, it is widely accepted as a substitute for new household refrigerators and freezers. The main caveat is that isobutane is flammable, so its use is governed by safety standards and proper design in appliances, but when those controls are followed, it is considered an acceptable option for new units. In contrast, older refrigerants like R22 are ozone-depleting and largely phased out; ammonia is highly efficient but toxic and not used in typical consumer fridges; R134a has a higher global warming potential, so while common, it isn’t favored in the sense of being the universal substitute described here.