What characteristic defines an indirect vented closed system?

An indirect vented closed system is characterized by its design that ensures refrigerant does not mix with the air stream. This isolation is a critical safety feature, as it prevents potential contamination of the air supply with refrigerants, which can be hazardous to health and the environment. By keeping the refrigerant contained within a closed loop, the system can operate efficiently while maintaining safety standards.

This ensures a reliable cooling or heating process without the risks associated with leaking refrigerants. The design reflects a thoughtful approach to mechanical systems, prioritizing safety and efficiency, making option B the defining characteristic of an indirect vented closed system.