In which scenario are smoke detectors not required in the return air system?

Smoke detectors are crucial for safety in buildings as they help recognize smoke and potential fire hazards. However, there are specific guidelines regarding their placement and requirements. In the given scenario, if area smoke detectors are present in the building, the code often allows for a reduction in further smoke detection requirements, including those in the return air systems.

Area smoke detectors can effectively monitor smoke levels and provide adequate warning to occupants, fulfilling the primary intent of smoke detection safety. Thus, if these detectors are installed, it is deemed sufficient to ensure safety without the need for additional detectors in the return air system. This indicates that the smoke detection needs can be met sufficiently through other means, streamlining the requirements for smoke detection in the mechanical systems of the building.

The presence of area smoke detectors allows for this flexibility, acknowledging that smoke detectors in the return air system may not provide significant additional benefit when the area is adequately covered by standalone detectors, thus justifying their absence.