What type of system provides HEPA-filtered ISO class 5 unidirectional air for compounding?

The correct choice is the restricted-access barrier system (RABS) because it is specifically designed to provide an ISO class 5 environment through HEPA-filtered air in a unidirectional airflow pattern. This type of system is utilized to enhance the safety and sterility of compounding by minimizing contamination risks while also allowing for more controlled access.

RABS includes equipment such as isolators or closed systems that create a barrier to protect the compounded products from environmental contaminants. They often feature glove ports for manipulation of materials within the system, ensuring that the compounded preparations are made in a sterile and controlled setting.

Other systems mentioned, such as laminar flow hoods, do provide a sterile environment through HEPA filtration and unidirectional airflow, but they do not have the same enhanced barrier feature that RABS offers. A unidirectional airflow chamber is a more general term for systems that provide unidirectional airflow but might not be classified strictly as RABS. A negative pressure room is designed to contain hazardous substances and is not specifically intended for sterile compounding.

Thus, the unique characteristics of RABS make it the most appropriate choice for compounding sterile preparations in a highly controlled and contamination-free environment.