Interpretation #6596

The definition of "Terminal" in Chapter 13 of the FBC- Building (the source of Sections 603.5.6.6 and 603.6 of the FBC- Mechanical) reads as follows: "A device by which energy from a system is finally delivered, e.g., registers, diffusers, lighting fixtures, faucets, etc." Where the terminal fitting is attached to the building envelope (joists) and the diffuser is attached to the terminal fitting (by screws/mechanical device), it is mechanically attached. Further, Section 603.6.2 requires that terminal fittings be sealed with mastic or gaskets. This is important because of air leakage from around the terminal device. Another issue is whether a grille (register) requires independent support. There are more and more of the industrial look designs with no ceilings. In these cases the registers are attached directly to a rigid duct with no tie wires or other support for the terminal device. In these cases, the duct provides the required support for the register, grille, diffuser. The key is a mechanical attachment to the duct and the duct system being properly supported.