When pipe or conduit penetrates a duct or hood, the penetration shall have a ___________ or shall be sealed by a listed device.

• A. Liquidtight continuous external weld
• B. Firestop mortar
• C. Threaded coupling
• D. Silicone sealant

Answer: (A)

Sealing penetrations in a duct or hood is about preserving the fire barrier and preventing grease and flame from leaking around a pipe. The most reliable method is a liquidtight, continuous external weld around the pipe where it passes through the duct. This creates a seamless seal on the outside of the duct, eliminating openings for grease-laden air and maintaining the fire-resistance rating of the assembly. If welding isn’t possible, a listed device designed for duct penetrations can be used to seal the gap, but it must be installed per its listing. Other options like firestop mortar, threaded couplings, or silicone sealant don’t provide the same durable, heat- and grease-resistant seal for hood penetrations.