What should hazardous drug transport bags never be placed in?

Hazardous drug transport bags should never be placed in containment secondary engineering controls because these controls are designed to contain and protect against the exposure and release of hazardous substances within a controlled environment. The primary function of containment secondary engineering controls, such as ventilated compounding aseptic isolators (CAIs) or compounding aseptic containment isolators (CACIs), is to maintain a sterile environment and isolate hazardous drugs from the personnel and the surrounding area. Placing hazardous drug transport bags in these systems would compromise not only the integrity of the drugs being transported but also the effectiveness of the engineering controls themselves.

The other choices, such as biological safety cabinets, refrigerators, and transfer trays, are appropriate for specific conditions and functions. Biological safety cabinets are designed for handling hazardous materials safely, refrigerating hazardous drugs ensures that they remain stable, and transfer trays aid in safe transport without compromising sterility. Thus, containment secondary engineering controls are unsuitable for temporary holding or transport of hazardous drugs, making that the correct answer.