Getting a kitchen exhaust approved in WA

General guidance, not legal advice. Council guidelines change, so read the current one for your council and ask the building surveyor which NCC edition the permit uses. Clauses are quoted from NCC 2022 Volume One, AS 1668.2-2012 (Amendments 1 and 2), AS 4674-2004, FSANZ Standard 3.2.3 and the WA Environmental Protection (Noise) Regulations 1997.

1. Two approvals, one exhaust
2. When a hood is required
3. Which edition of AS 1668.2
4. Where WA councils differ
5. What to lodge
6. Do not fabricate before approval
7. Who certifies
8. Noise from the roof fan
9. Why drawings come back

01Two approvals, one exhaust

The building permit

A canopy, grease duct and roof fan are building work, and many WA council guidelines say a building permit is needed where exhaust canopies are installed (Fremantle, Vincent, Melville, Canning, South Perth, Kalamunda and Perth among them). The permit is assessed against the National Construction Code. NCC 2022 Volume One Clause F6D12 requires a commercial kitchen to have a kitchen exhaust hood complying with AS 1668.1 and AS 1668.2 once the cooking equipment passes set power inputs (Section 02). The registered building surveyor checks the design against those Standards.

The health approval

The food business registers with, or notifies, the local government under the Food Act 2008, and the council's environmental health officer (EHO) assesses the fit-out. The test is FSANZ Food Standards Code Standard 3.2.3, clause 7: food premises must have sufficient natural or mechanical ventilation to effectively remove fumes, smoke, steam and vapours. The Standard sets no numbers, so most councils publish a guideline, usually pointing to AS 1668.2, and the EHO inspects before the business trades.

02When a hood is required

Clause 3.3.1(b) exempts commercial coffee machines, microwaves and similar low-power equipment used infrequently or solely for reheating, space heating and domestic apparatus. Electric does not exempt a fryer: two electric fryers still need a canopy, a grease duct and a fan. What electric removes is the gas side, not the hood.

The 2024 edition of AS 1668.2 changes the trigger. Government guides that reproduce it (ACT Health, August 2025, and Campbelltown City Council in NSW) call for a hood over a single deep fryer above 3.6 kW, and over cooking process Types 3 to 6 above 3.6 kW combined when they are within 2 m of each other, which is tighter than the NCC 8 kW figure. Check this if the building permit is assessed under NCC 2025.

03Which edition of AS 1668.2 applies

NCC 2022 calls up AS 1668.2-2012 with Amendments 1 and 2. NCC 2025 calls up AS 1668.2:2024. WA adopted NCC 2025 on 1 May 2026 with a transition: a building permit application may still use NCC 2022 until 30 April 2027, but one application cannot mix the two. Agree the edition with the building surveyor before the exhaust is designed, not after.

Council guidelines are older. Across the 22 WA councils we checked, AS 1668.2 is cited as the 1991 edition (Cockburn, Wanneroo, Gosnells, Victoria Park, Bayswater), the 2002 edition (Fremantle, Melville, Canning, Mandurah, Armadale), the 2012 edition (Vincent, South Perth, Nedlands) or with no date (Perth, Swan, Bunbury). None named the 2024 edition yet.

04Where WA councils differ

Every guideline with a ventilation clause hands the design itself to AS 1668.2. They differ in how many numbers they add on top, and a few of those numbers go beyond the Standard.

Council numbers that go beyond the Standard

• Discharge height. At least 3 m above a flat roof or 1 m above the ridge of a pitched roof (Cockburn, Wanneroo, Gosnells, Victoria Park, Melville, Nedlands). Some allow a relaxation more than 15 m from any higher structure, and Nedlands also for discharges of 1000 L/s or less. AS 1668.2-2012 writes that height for Type A effluent, and kitchen exhaust is Type B. Where the council's guideline sets it, design to it.
• Exhaust rate. At least 0.38 m³/s per m² of appliance top surface (Cockburn, Wanneroo).
• Make-up air. At least 10 air changes per hour by mechanical supply, or permanent natural ventilation, from an uncontaminated source (Cockburn, Wanneroo).
• Capture velocity at the hood face by type of cooking, up to 0.6 m/s for a wall canopy over flame cooking (Nedlands).
• Grease duct. Galvanised steel 1.2 mm or stainless 0.9 mm, with cleaning points no more than 3 m apart and at every change of direction (Nedlands; cleanouts also Cockburn and Wanneroo). These repeat the AS/NZS 1668.1 and AS 4254.2 duct rules; cleaning the ducts at least every six months (Cockburn, Wanneroo) is the council addition.
• Gutter overhang of 300 mm beyond woks, salamanders and open-flame charcoal or solid fuel (Nedlands). For salamanders this is more than AS 1668.2-2012 asks.

Councils that give discharge numbers repeat the Standard's 6 m from property boundaries, air intakes and openings; Cockburn, Wanneroo and Nedlands also repeat vertical discharge at 5 m/s or more. More on the roof layout in 7 design decisions that set the cost of a kitchen exhaust.

05What to lodge

Most council guidelines ask for a mechanical exhaust ventilation plan with the application, drawn at 1:50 in Fremantle, Vincent, Melville, Canning, South Perth, Armadale and Kalamunda. Vincent and Stirling also want sectional elevations. South Perth wants the outlet shown against air intakes and neighbouring properties, Rockingham wants the outlet location and performance, and Bunbury asks for the specifications of all cooking equipment.

A design package that answers the surveyor and the EHO at the same time covers:

• Equipment schedule: every appliance under a hood, with make, model and kW or MJ/h
• Hood plan and section: length, width, overhang on each side, lower edge above the floor and above the cooking surface, filter height above the cooking surface
• Exhaust rate calculation with the clause and edition, plus the council's own check where it sets one
• Grease duct: route, size, material and thickness, access panels
• Fan duty in L/s at Pa, position and speed control
• Roof plan: discharge direction and velocity, distances to boundaries, air intakes and openings
• Make-up air: quantity, intake position, where it enters the kitchen, interlock with the exhaust
• Gas appliances: how their air supply is provided and interlocked (the licensed gasfitter installs and certifies the gas work)
• Noise estimate where homes are close (Section 08)

06Do not fabricate before approval

Nedlands asks for the plans and specifications of all exhaust hoods to be approved before construction or installation. Rockingham issues a conditional approval first, construction may only start after it, and fixtures that do not comply have to be refitted. Victoria Park wants the specifications before installation, and Cockburn, Wanneroo and Gosnells want plans lodged with Health before the canopy is built. A canopy made before approval is the most expensive way to learn the council wanted a bigger overhang.

07Who certifies

Most WA guidelines ask for written certification that the system meets the performance criteria, without naming a profession. Some are specific. Wanneroo has a mechanical services engineer certify the installation. Mandurah accepts written certification from the installer or a ventilation engineer. Vincent accepts a suitably qualified installer or builder, and its fit-out form asks for a certificate of compliance against the BCA, AS/NZS 1668.1 and AS 1668.2. Perth wants the certificate before the business opens.

In practice two documents carry it: the design documentation from the engineer who designed the system (what was designed, to which clauses and edition), and the installation and commissioning certificate from the mechanical contractor, with the airflows measured on site. Ask the council whose signature it accepts before you engage anyone.

08Noise from the roof fan

The neighbours hear the fan too. The WA Environmental Protection (Noise) Regulations 1997 set assigned levels at the premises receiving the noise:

A tonal hum adds a 5 dB penalty. A bakery that starts at 4 am is judged against the night level, so fan selection, speed control and position on the roof matter. Melville's guideline notes that an acoustic report may be requested.

09Why drawings come back

These are the items we check first on every design, taken from the council guidelines and the Standard. They are our checklist, not a council statistic.

• A discharge within 6 m of an air intake, openable window or property boundary, or one that does not discharge vertically
• A fryer, salamander or dishwasher left outside any hood
• No discharge height shown in a council that sets one (Section 04)
• No make-up air, or a supply grille blowing across the front of the hood
• Equipment changed after approval: AS 4674-2004 Cl 2.5.1 says equipment installed later must not impair the exhaust system
• No written certification with the application

QUESTIONSWhat builders and owners ask

Scope: I design and calculate kitchen exhaust systems as a mechanical engineer (MIEAust). The mechanical contractor supplies, installs, commissions and certifies the system, and the licensed gasfitter installs and certifies the gas work. More on the service: kitchen exhaust, ventilation and air conditioning design in Perth.