How to Install Restaurant Kitchen Ventilation and Exhaust Ducts

How should restaurant kitchen ventilation and exhaust ducts be installed? Exhaust performance decides whether a foodservice kitchen can run properly. CHINENG shares installation knowledge below.

Installation methods for kitchen exhaust ducts

1. Do not place demountable duct joints inside walls or corridor floor slabs.

2. Embed hangers and expansion bolts accurately and firmly; keep embedded parts unpainted and free of oil. Unless otherwise designed, support spacing for uninsulated ducts is:

1) Horizontal: 4 m when diameter/side < 400 mm; 3 m when ≥ 400 mm.

2) Vertical: 4 m, with at least two fixings per riser.

3) Insulated ducts follow the design.

4) Do not place supports at outlets, valves, or access doors; do not hang directly from flanges; add anti-sway fixings where needed.

5) Fire dampers and motorized dampers need dedicated hangers.

6) Flange gaskets about 3–5 mm thick must not protrude into the duct; nuts sit on the same side.

7) Horizontal levelness ≤ 3/1000, total deviation ≤ 20 mm; verticality ≤ 2/1000, total deviation ≤ 20 mm.

8) Valve operators must be accessible; blades insert with airflow; fire-damper fusible links are fitted after system install.

9) Outlets must be flush, accurate, free-moving, and firmly connected. Flexible connectors should be properly tensioned, not twisted.

10) Sheet-metal duct fabrication includes fittings, flanges, stiffeners, and hangers, but not floor-standing cross-span supports.

4. Flexible ducts may be metal, coated fabric, polyester, PE/PVC film, aluminum foil, and similar.

5. Turning vanes use the same work item whether single or double-blade.

6. For tapered uniform-supply systems, use average diameter/perimeter with labor factor 2.5.

Restaurant kitchen exhaust design notes

1. Keep horizontal grease ducts short—generally under 15 m—with about 2% slope and a cleanout at the end.

2. Duct velocity should not be below about 10 m/s so grease does not settle easily.

3. Branch ducts to hoods need balancing dampers. Main duct velocity is often 8–10 m/s; hood throat velocity about 4–5 m/s.

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