A refrigerant that can be used as a direct service 'drop-in' substitute for R-22 in a small appliance is:

Prepare for the HVAC EPA Type I Test. Study with flashcards and multiple choice questions, each with hints and explanations. Get ready to excel in your exam!

Direct service drop-in substitutes must be compatible with how the system was designed—its pressures, lubricating oil, materials, and seals. Small appliances that use R-22 are built around mineral oil and a specific pressure range. The refrigerants listed differ in key ways: R-410A operates at much higher pressures and needs different components and oil; R-134a typically uses a different oil and gasket materials and isn’t compatible with mineral oil without a full retrofit; R-141b also has different lubrication and material compatibility and isn’t a simple swap. Because of these mismatches, none of these options can be used as a direct drop-in replacement for R-22 in a small appliance. The correct approach is a proper retrofit with an approved refrigerant and component/oil changes, or choosing a different appliance designed for a compatible refrigerant.