What type of assembly should flexible ducts and air connectors not pass through?

The correct answer is that flexible ducts and air connectors should not pass through a fire-resistance-rated assembly. Fire-resistance-rated assemblies are designed to contain fire and prevent its spread between different areas within a building. This rating is crucial for maintaining the integrity of fire barriers, as they help control the movement of smoke and heat during a fire event.

When flexible ducts and air connectors are introduced into such assemblies, they can create a potential pathway for smoke and flames, thereby undermining the assembly's purpose. To maintain adequate safety and ensure proper compliance with fire codes, these types of ducts should be avoided in fire-resistance-rated assemblies or should be properly protected if they must penetrate them.

In contrast, non-combustible assemblies, ground assemblies, and ventilation assemblies may not have the same stringent requirements as fire-resistance-rated assemblies, allowing for the inclusion of flexible ducts under specific conditions.