Commercial Kitchen Canopy Sizing Guide

Most commercial kitchen canopy complaints — smoke drifting into dining rooms, sticky walls, staff overheating, fire insurance issues — trace back to a single root cause: the canopy is the wrong size for the cooking equipment beneath it. An undersized canopy can't capture what's coming off the stove. An oversized canopy pulls too much conditioned air out of the kitchen, driving up energy costs and creating make-up air problems.

This guide walks through commercial kitchen canopy sizing the way we size canopies at NXT GEN: starting with the equipment list, applying the AS 1668.2:2024 rules, and ending with a number you can take to a fabricator. If you want the full regulatory context first, our AS 1668.2:2024 Victorian regulations guide covers the standard in depth.

The AS 1668.2 sizing rules in plain English

AS 1668.2:2024 — the current edition of Australia's mechanical ventilation standard — sets three things that every commercial kitchen canopy has to nail: the cooking process type, the overhang distance, and the make-up air balance. Every other decision (filter type, fan selection, duct diameter) flows from those.

Cooking process type

The first decision is identifying which of the eight cooking process types in clause 3.4.2.3 your equipment falls into. The type determines everything that follows — different types have different overhang requirements, different exhaust rates, and in some cases different fire suppression rules. Mixed-equipment cooking lines must be sized to the worst-case process type present under the canopy.

Overhang distance

The canopy must extend beyond the edge of the cooking surface on every side that isn't sealed against a wall. AS 1668.2:2024 Table 3.1 specifies the minimum overhang separately for the front and the sides — they're not always the same number. The overhang creates the capture area that draws rising heat, smoke, grease, and steam into the filters instead of letting them escape into the room.

Make-up air

Every cubic metre of air you exhaust has to be replaced with a cubic metre of fresh air coming in. Make-up air supply must equal 65–85% of the exhaust flow, with the remainder drawn from adjacent spaces via transfer air. Get this wrong and you create negative pressure, which pulls air backwards through your flue, disrupts combustion on gas appliances, and slams every self-closing door in the building.

The eight cooking process types under AS 1668.2:2024

AS 1668.2:2024 clause 3.4.2.3 classifies cooking equipment into eight process types based on what it emits — grease, heat, steam, vapour, embers. Identifying the type correctly is the foundation of every sizing decision that follows.

Hood overhang requirements: AS 1668.2:2024 Table 3.1

Once you've identified the cooking process type, AS 1668.2:2024 Table 3.1 sets the minimum hood overhang on the front and on the sides. Note that front and side overhangs are specified separately — they're not always equal. Overhang only applies on sides that aren't pressed against a wall.

A few important details from the standard:

• Island hoods get the same rear overhang as the front. If your canopy is over a free-standing cooking island, every side that isn't pressed against a wall gets the front overhang value. There's no "back" on an island — every side is a front.
• The overhang is measured to the inside of the capture zone or gutter. Not to the outer edge of the canopy body — to the working capture area. Cheap canopies sometimes claim "300 mm overhang" measured to the outer edge of trim, which doesn't comply.
• Process Type 1 has a special exception covered in clause 3.4.4 — some specific Type 1 equipment (low-emission) may be exempt from the standard hood requirement under defined conditions.
• Process Type 8 (solid fuel) requires 300 mm from any opening through which embers can escape. If an oven door opens and creates a new opening, the 300 mm is measured from there, not the static perimeter.

Worked example: a wall-mounted café cooking line

A typical Melbourne café has an 1800 mm cooking line against a back wall: a four-burner gas range (Type 2), a flat-top griddle (Type 2), and an under-counter convection oven (Type 2). All three appliances are Process Type 2.

Required canopy length:

• Cooking line length: 1800 mm
• Plus 150 mm side overhang on the left: +150 mm
• Plus 150 mm side overhang on the right: +150 mm
• Minimum compliant canopy length: 2100 mm
• Front overhang: 150 mm beyond the front edge of the cooking equipment

In practice we'd specify a 2100 mm or 2400 mm canopy from our canopy shop. Going up to 2400 mm gives extra capture margin, which matters as equipment sometimes shifts during service.

Worked example: a wok station

A 1200 mm wok station with two large wok burners (Process Type 6) against a back wall.

• Cooking line length: 1200 mm
• Plus 600 mm side overhang on the left: +600 mm
• Plus 600 mm side overhang on the right: +600 mm
• Minimum compliant canopy length: 2400 mm
• Front overhang: 600 mm beyond the front edge

A 1200 mm cooking surface needs a 2400 mm canopy with a 600 mm depth allowance for front overhang — Type 6 is by far the most demanding category in the standard, which is why purpose-built wok canopies are bigger than they look at first.

Worked example: a mixed cooking line with a char grill

A 2400 mm cooking line with a flat-top griddle (Type 2), a deep fryer (Type 4), and a char grill (Type 5) all under one canopy. AS 1668.2 requires sizing to the worst-case process type — Type 5 in this case (Type 5 has higher overhang than Type 4).

• Cooking line length: 2400 mm
• Worst case is Type 5: 300 mm side overhang
• Plus 300 mm side on left + 300 mm side on right: +600 mm
• Minimum compliant canopy length: 3000 mm
• Front overhang: 300 mm
• Plus: Type 5 cooking requires factory-fitted fire suppression

This is why a double filter bank canopy earns its cost on mixed lines with high-grease and high-heat equipment under the same hood.

Make-up air: the other half of the sizing equation

A canopy only works if replacement air can get into the kitchen as fast as the fan pulls it out. AS 1668.2 requires make-up air equal to 65–85% of exhaust flow — the remaining 15–35% is transfer air from adjacent conditioned spaces.

In a retrofit, this is often the hardest problem to solve because existing buildings weren't designed for it. Options include:

• Dedicated make-up air unit — a supply fan drawing outside air through a filter directly into the kitchen
• Door and window transfer — only viable in small kitchens with well-sealed buildings
• HVAC supply integration — routing additional supply air through the existing air-conditioning system
• Tempered make-up air — heating or cooling incoming air to avoid drafts, standard for Melbourne fit-outs

Insufficient make-up air is the number one cause of "my canopy doesn't work" callouts — not fan size, not hood design. If your kitchen doors slam when the fan turns on, you have a make-up air problem, not a canopy problem.

Signs your canopy is the wrong size

A wrongly sized canopy tells you. Most of these symptoms appear within the first two weeks of trading and indicate specific sizing problems:

• Smoke escapes to the sides — canopy is too short or the side overhang is inadequate
• Grease drips onto the floor in front of the cookline — front overhang is too short or canopy depth is too shallow
• Walls and ceilings near the canopy get sticky quickly — exhaust flow rate is too low for the cooking type
• Room feels drafty or doors slam shut — exhaust is oversized relative to make-up air
• Gas burners misbehave or flames lift — negative pressure from insufficient make-up air disrupting combustion
• Staff complain of heat build-up — canopy isn't capturing thermal load, probably undersized for a Type 5 or 6 process
• Fire insurance quote is unexpectedly high — insurer has flagged compliance concerns

The fix depends on which symptom you're seeing. Sometimes it's as simple as upgrading the fan to a larger capacity. Sometimes the canopy itself has to be replaced because it's physically too small for the process type. A 30-minute site inspection usually identifies which.

Getting a compliant commercial kitchen canopy size

The quickest path to a correctly sized canopy is sharing five pieces of information with your manufacturer up front:

• A cooking equipment list with make, model, and kW or MJ/h rating of every appliance
• Cooking line dimensions — total length along the wall and depth from wall to front edge
• Ceiling height — canopies normally sit 2.0–2.1 m above the floor, requiring a minimum 2.4 m ceiling
• Wall configuration — whether the cooking line is against a back wall, in a corner, or in an island
• Process types in play — especially whether anything is Type 5 (char-grills), Type 6 (woks), or Type 8 (solid fuel)

At NXT GEN we use these five pieces of data to produce a compliant size with the correct front and side overhangs, flow rate, make-up air requirement, and fan pairing. We manufacture all our canopies in Coburg North and install across metro Melbourne, Geelong, Ballarat, and Bendigo. For the cost side of canopy sizing, see our 2026 buyer's guide.

Commercial kitchen canopy sizing — FAQs

What size commercial kitchen canopy do I need?

It depends on your cooking process type under AS 1668.2:2024 Table 3.1. For a typical Type 2 café cookline (gas ranges, fry tops, ovens) you need 150 mm front overhang and 150 mm side overhang. For a Type 5 char grill or Type 4 deep fryer you need 300 mm. For a Type 6 wok station you need 600 mm. The canopy length is the cookline length plus the side overhang on each open side. The canopy depth must accommodate the front overhang plus the equipment depth.

What is the minimum overhang for a commercial canopy?

AS 1668.2:2024 Table 3.1 sets the minimum hood overhang by cooking process type. Process Type 2 and 3 require 150 mm front and side. Process Types 1, 4, and 5 require 300 mm front and side. Process Type 6 (woks) requires 600 mm front and side — the largest overhang in the standard. Process Type 7 (multi-stack ovens) requires 450 mm front and 300 mm side. Type 8 (solid fuel) requires 300 mm from any opening through which embers can escape.

How are AS 1668.2:2024 cooking process types classified?

AS 1668.2:2024 clause 3.4.2.3 classifies cooking equipment into eight process types based on emissions. Type 1 is non-greasy heat or steam (dishwashers, warming cabinets). Type 2 is grease with moderate heat (gas ranges, fryers). Type 3 is steam and grease (steam kettles, pasta cookers). Type 4 is high grease (deep fryers, bratt pans). Type 5 is high heat (char grills, BBQs, tandoors). Type 6 is very high grease and vapour (woks, Oriental cooking tables). Type 7 is large surges of contaminants (multi-stack ovens). Type 8 is smoke and embers (solid fuel cooking).

What if my cooking line has multiple process types?

Size the canopy to the worst-case process type present under the hood. A line with a Type 2 range, Type 4 fryer, and Type 5 char grill all under one canopy is sized to Type 5 — meaning 300 mm front and side overhang. The single highest-overhang requirement applies to the whole canopy, not just the section above that equipment.

Are island canopies sized differently?

Yes. AS 1668.2:2024 specifies that island hoods get the same rear overhang as the front overhang. There's no "back" on an island — every side is a front, so the larger of the front/side values applies on all four sides. This is why island canopies are physically larger and more expensive than equivalent wall-mounted units.

What happens if my canopy is too small?

An undersized canopy fails in three ways: it fails council inspection so you cannot legally open, it voids your fire insurance because it doesn't meet AS 1668.2, and it physically cannot capture the heat and grease your cooking produces — leaving staff working in smoke and walls getting greasy. None of these problems can be fixed cheaply after installation. Getting the sizing right up front is the single most important decision in the whole ventilation project.

Do canopies need to be certified by an engineer?

For most Victorian commercial fit-outs, your building surveyor checks AS 1668.2 compliance as part of the building permit — not a separate engineer. For complex installations (large kitchens above 1,000 L/s, treated exhaust pathways, or unusual building configurations), the building surveyor may require a mechanical engineer's design certification. A quality canopy manufacturer provides the documentation your surveyor needs.