If your kitchen hood is the wrong size, you can end up with smoke spill, grease build-up, failed approvals, and higher running costs. I’d keep the answer simple: measure the full cookline, add the right overhang, size airflow to the highest-duty appliance, and then check layout, make-up air, and fire code before buying anything.
Here’s the short version:
- Measure every appliance in mm: width, depth, gaps, and clearances.
- Add canopy overhang based on cooking load:
- Light duty: around 150 mm
- Medium duty: 300 mm front, 150 mm sides
- Heavy duty: up to 300 mm on exposed sides
- Set airflow with Q = A × V
- Light duty: 0.15–0.25 m/s
- Medium duty: 0.25–0.35 m/s
- Heavy duty: 0.35–0.50 m/s
- Solid fuel: 0.50–1.00 m/s
- Size for the highest-load appliance if one hood covers mixed equipment.
- Island hoods usually need 20–30% more airflow than wall hoods.
- Replace 80–90% of extracted air with make-up air.
- In UAE summer conditions, adding 15–20% airflow may be needed when ambient temperature goes above 35°C.
- For grease-producing cooking, use a Type I hood with UL 300 fire suppression.
A quick example: a 2,400 mm × 900 mm hood has an area of 2.16 m². At 0.30 m/s, that works out to about 2,333 m³/h. That gives you a clear starting point before fan and duct checks.
| Check | What I’d confirm |
|---|---|
| Hood footprint | Covers the full cookline with the right overhang |
| Airflow | Based on duty class and hood area |
| Layout | Wall, corner, or island changes airflow demand |
| Hood type | Type I for grease, Type II for heat/steam only |
| Make-up air | 80–90% of extract air |
| Compliance | UAE Civil Defence, municipality, fire suppression, duct details |
Bottom line: the hood size is not just the canopy length. It is the canopy footprint + airflow rate + layout + code fit. I’d treat all four as one decision.
Kitchen Exhaust Hood Sizing Guide: Duty Classes, Overhang & Airflow
Step 1: Measure the cooking line and set the hood dimensions
Start with the cooking line as installed. Before you check any hood spec, map the exact footprint of every appliance in the line.
Measure appliance widths, depths, and gaps across the full lineup
Go unit by unit - grills, fryers, ranges, combi ovens, and anything else in the suite. Record the width and depth of each appliance in mm, along with any gaps and door clearances. That gives you the hood length and the deepest hood depth you’ll need.
Apply canopy overhang rules for wall and island hoods
Once you’ve got the equipment footprint, add the canopy overhang. For a wall-mounted hood, the rear wall helps hold the thermal plume, so the overhang is only needed at the front and the two open ends. For an island hood, every side is open, so the overhang needs to be added on all sides.
| Equipment Type | Duty Class | Front Overhang | Side / End Overhang |
|---|---|---|---|
| Ovens, Steamers, Bakery | Light | 150 mm | 150 mm |
| Fryers, Griddles, Ranges | Medium | 300 mm | 150 mm |
| Charbroilers, Woks, Grills | Heavy | 300 mm | 300 mm |
| Solid Fuel (Wood / Charcoal) | Extra-Heavy | 300 mm+ | 300 mm+ |
These dimensions set the hood footprint. After that, you can move to airflow.
Use end panels or partial enclosure when space is tight
If the kitchen layout won’t allow the full recommended overhang, end panels are a practical way around the problem. A stainless steel end panel on the open side helps block cross-drafts and improves capture. This is especially useful on heavy-duty lines, where charbroilers or woks sit at the end of the cooking suite.
With the hood footprint fixed, use it to work out the extraction airflow in the next step.
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Step 2: Calculate the extraction airflow you need
Once the hood footprint is fixed, the next job is to work out how much air the system must move.
Choose the duty class and capture velocity
Every appliance throws off a plume of heat, grease, and vapour. Capture velocity is the air speed needed at the hood edge to pull that plume in.
The duty class of the equipment tells you what capture velocity to use. Light-duty equipment, such as ovens, steamers, and kettles, needs 0.15–0.25 m/s. Medium-duty cooking lines - griddles, fryers, and gas ranges - need 0.25–0.35 m/s. Heavy-duty kit like charbroilers, woks, and grills needs 0.35–0.50 m/s. Solid-fuel appliances that burn wood or charcoal fall into the extra-heavy class and need 0.50–1.00 m/s.
If one hood covers a mix of appliances, size it for the highest-duty item under that hood.
Calculate airflow with Q = A × V and convert it for local specifications
Use the footprint from Step 1 and apply Q = A × V, where Q is airflow rate, A is the hood face area (length × width, in m²), and V is the target capture velocity in m/s. This gives airflow in m³/s. Multiply by 3,600 to convert it to m³/h, or by 1,000 to convert it to L/s.
Here’s what that looks like in practice:
A 2,400 mm × 900 mm hood over a medium-duty fryer line has a face area of 2.16 m².
At a capture velocity of 0.30 m/s, Q = 2.16 × 0.30 = 0.648 m³/s, which is about 2,333 m³/h or 648 L/s.
If the cooking line includes mixed appliance types, use the airflow based on the most demanding appliance in that run.
In UAE kitchens, it also makes sense to add 15–20% to the calculated airflow when ambient temperature goes above 35°C.
Adjust for make-up air, duct losses, and fan selection
Extraction is only one side of the equation. You also need to replace most of that air, or the kitchen can end up fighting itself. As a rule, replace 80–90% of the extracted air with tempered make-up air so the space stays under slight negative pressure.
Fan sizing also needs to account for duct losses. And the duct velocity should stay within 2.5–7.6 m/s.
For Dubai or Abu Dhabi approvals, submit certified airflow calculations and make sure the system includes UL 300 fire suppression.
Step 3: Match hood size to your equipment and kitchen layout
Now take your airflow numbers and test them against the actual cookline and the way the kitchen is set up. On paper, the numbers may look fine. In practice, the appliance mix and hood position can change everything.
Heavy-duty lines: grills, fryers, charbroilers, and wok stations
Heavy-duty appliances shape the hood design because they create the highest extraction demand. If you have a charbroiler or wok at one end of the line, that one item can set the hood requirement for the whole run. Start by sizing around the highest-load appliance, then make sure the hood covers the full line.
Use the heavy-duty overhang range from Step 1. These appliances need the widest canopy coverage. Grease-producing equipment such as fryers, charbroilers, griddles, and wok stations needs a Type I hood with baffle filters, grease collection features, and automatic fire suppression. If the canopy is too small, capture drops and compliance becomes harder.
Light-duty lines don’t work the same way, so the hood class may shift based on the equipment mix.
Light and medium-duty lines: ovens, bakery equipment, and mixed cooking suites
Ovens and bakery lines are lower-grease loads. That means they use lower extraction rates and Type II hoods for dry-heat use only. A light-duty oven line will often sit around 0.25–0.38 m/s capture velocity.
Here’s the part that catches people out: if a bakery line includes even one gas griddle or another grease-producing appliance, the whole hood must be sized to the highest-duty item on that line and treated as Type I.
Wall, corner, and island layouts and what changes with each
Layout changes the answer even when the appliance list stays the same. A wall-mounted canopy gets help from the back wall, which acts like a natural baffle and cuts the airflow needed for a given appliance load. That’s why wall layouts are usually the most efficient choice when the cookline sits against a solid surface.
An island canopy is a different story. It’s open on all sides, so it’s more exposed to cross-drafts and usually needs about 20–30% more extraction than a similar wall-mounted setup. It also needs more canopy coverage on every exposed side.
A corner hood sits somewhere in the middle. It gets some help from the walls, but the open sides still matter. End panels or partial enclosure can help control that exposure.
| Layout | Airflow relative to wall hood | Key sizing consideration |
|---|---|---|
| Wall-mounted | Baseline | Standard overhang on exposed sides |
| Corner | Moderate increase | End panels can help on open sides; two walls aid containment |
| Island | About 20–30% higher | Largest canopy; overhang required on all exposed sides |
Whatever the layout, keep the hood away from open doors, supply air diffusers, and high-velocity HVAC vents. Air disturbance around the canopy cuts capture efficiency.
Conclusion: Sizing checks to complete before you buy or install
Before you buy anything, make sure the hood fits the cooking line, duty class, airflow load, and the kitchen layout. Then check that the design meets UAE fire and municipality rules. Do this before you order equipment or release drawings.
In the UAE, the design should be checked against UAE fire code, NFPA 96, and local municipality rules. You also need Civil Defence-approved drawings in place before procurement starts.
Final checklist for owners, operators, and project teams
Check each point below before ordering or installing. If even one item is missing, stop procurement until the design is fixed.
- Appliance schedule confirmed: Every appliance on the line is listed with its exact width, depth, and duty class: light, medium, heavy, or extra heavy.
- Hood type selected: Use Type I for any line with grease-producing equipment. Use Type II only for heat and steam.
- Hood dimensions set: Width and depth include the right canopy overhang of 150 mm to 300 mm on all exposed sides. For island layouts, allow for the 20% to 30% higher airflow demand.
- Target airflow confirmed: Confirm the target airflow in m³/h and CFM. Heavy-duty lines should sit within the required range.
- Make-up air sized: MUA replaces 80% to 90% of the exhausted volume so the kitchen keeps slight negative pressure.
- Duct route planned: The route includes straight runs, access panels, and fire-rated ductwork.
- Fire suppression integrated: A UL 300 or LPCB-certified wet chemical system is in place, with nozzles located over all high-risk appliances.
- Civil Defence approval obtained: Civil Defence drawings are approved before procurement begins.
FAQs
How do I choose between a Type I and Type II hood?
Choose the hood based on what your equipment puts out.
Use a Type I hood for appliances that produce grease-laden vapours and smoke, such as fryers, griddles, ranges, and broilers. These setups need grease filters, fire suppression, and welded, liquid-tight ductwork.
Use a Type II hood only for equipment that produces heat, moisture, or odours without grease, such as dishwashers or steamers. Always check with local authorities. If you classify the hood the wrong way, you can breach code and increase fire risk.
What happens if your exhaust hood is too small?
If your exhaust hood is too small, it may not pull out smoke, heat, and grease vapours the way it should. When that happens, airflow suffers, grease starts to build up, the fire risk goes up, and smoke or cooking smells can drift into dining areas.
That spillover creates problems fast. The kitchen gets hotter and more uncomfortable for staff, which can slow people down during busy service. On top of that, it may lead to trouble during UAE fire and safety inspections.
Do I need a different hood size for an island cookline?
Yes. Island cooklines need different sizing from wall-mounted hoods because they hang from the ceiling and don’t get the same wall-capture effect.
That changes the job of the hood. Instead of pulling fumes in from one main direction, it needs to support 360-degree capture around the cooking line.
In practice, the hood should be larger than the cooking equipment. A common guide is to extend it by 150–300 mm beyond the front and by at least 150 mm on each side.
You’ll also usually need a higher extraction rate. Open-plan layouts are more exposed to cross-draughts, so the system has to work harder to contain heat, smoke, and grease-laden air.
