Existing applicable codes and standards for connecting an exhaust duct to a Type I restaurant exhaust hood or restaurant hood system are set to ensure compliance with codes and standards for connections, cleaning access, materials, drains, welding, and other provisions.

Still, there are food service facilities and fire scenes that operate on unlisted, welded on-site ducts. This results in problems of the integrity of the weld, the stability of the restaurant hood system against exposure to high temperatures, poor connections between exhaust ducts and hoods, improper penetrations of fire-rated barriers, insufficient duct clearance, non-compliance with drainage means and required slope, and lack of cleaning access panels.

As a solution, improvements were made on the materials and procedures used in installing a restaurant hood system and ducts.

To Improve Duct Integrity

A pressure washer is used in a duct washing procedure to determine leaks in ducts and access.

Previously, duct leakage was evaluated using air pressure test. But an engineer discovered that the length of a duct can be airtight but not liquid tight, resulting in leaks and fireballs.

To Improve Duct Stability

Codes and standards for welded ducts have been changed to ensure that ducts can hold up to extreme internal and external fire exposures. The UL Standards 1978 and 2221 require this specification to be met by both listed and unlisted duct insulation.

To Prevent Fires in Your Restaurant Hood System

The use of factory-built listed ductwork is specified instead of unlisted ducts as this offers several advantages.

Listed duct products conform to listing specifications and are subject to approved inspection and sampling. Even when on-site labor falls short of the standards, quality of materials is guaranteed because of highly trained factory labor.

Factory built connecting parts and adjustable telescopic ducts enhance installation versatility.

Field inspections are reduced when listed grease ducts are used instead of field-welded and field-wrapped ducts that require inspection after welding, after installation of the first insulation layer, and after the installation of the second insulation layer.

Listed ducts can withstand better and longer the rigors of grease duct fires than unlisted ducts.

Achieve better airflow with the use of a round restaurant exhaust duct instead of a rectangular duct.

When installed properly, listed ducts eliminate potential for leakage because all joints are tested to factory standards. Cleaning access doors, on the other hand, are tested to UL 1978.

The need for onsite welding is decreased which, in turn, increases safety during construction or remodeling.

Installation errors are minimized because listed duct products are already double wall insulated, eliminating the possibility of an overlapping layer.

Minimize the risk of ducts catching fire quickly when a stainless round duct is used. It is inherently stronger, more tolerant to cleaning agents, and keeps grease from adhering to the surface because of the smooth finish and lack of corners.

Listed ducts are less costly and easier to install even for multi-story installation because it can be stacked like a traditional boiler pressure stack flue and does not require many supports.

Summary

To ensure installation integrity and to prevent fire, the use of listed duct products, including a restaurant hood system, is highly recommended. In the most current specifications, they are the best materials for commercial applications.