Which of the following surfaces are flexible air connectors NOT allowed to pass through?

Flexible air connectors are components that allow for the connection of ductwork in a heating or cooling system while accommodating movement and expansion. According to the North Carolina Mechanical Code, these flexible connectors are generally restricted from passing through certain surfaces due to considerations of safety, integrity of the building structure, and air leakage prevention.

The surfaces through which flexible air connectors are not allowed to pass are walls, floors, and ceilings. These surfaces serve as critical barriers to maintain the thermal envelope and prevent the exchange of air between conditioned and unconditioned spaces. Allowing flexible air connectors to pass through these barriers could compromise the efficiency of the HVAC system and lead to potential air quality issues or structural integrity problems. By keeping these connectors from penetrating these surfaces, the code aims to ensure that the air distribution system functions correctly and adheres to safety standards.

In contrast, the other choices present scenarios or surface combinations that do not pose the same risks and are often more permissible under code regulations.