When are smoke detectors not required according to air distribution system capabilities?

The chosen answer is correct because smoke detectors are specifically intended to operate in environments where smoke could potentially spread. When air distribution systems are incapable of spreading smoke beyond the enclosing walls of a building, the necessity for smoke detectors is reduced. This is based on the principle that if smoke is contained within a defined area and does not infiltrate or propagate through the air distribution system, then there is a significantly lower risk of smoke affecting occupied spaces outside of that area, which diminishes the need for additional smoke detection.

In typical environments where smoke could spread, air distribution systems can facilitate the movement of smoke, which would make smoke detection crucial for safety and prompt response. Therefore, the lack of capability for these systems to spread smoke beyond walls implies that the conditions for smoke detector installation are not met, signifying that they may not be required.