Why the 1.2 m matters more than people expect
The prescriptive exhaust rate in Table 3.1 is Q = K × P × H, where H is the height of the hood above the cooking appliance. Height is a direct multiplier: raising a hood from 2000 to 2100 mm over a 900 mm appliance is about 9 % more air, every hour the kitchen runs, plus the make-up air to match. Above the 1.2 m limit you are outside the prescriptive method altogether.
| Heat source below the filter | Minimum clearance |
|---|---|
| Charcoal and similar open fires | 1350 mm |
| Naked flame, such as a gas stove | 1050 mm |
| Electric, or a fixed plate or pan above a gas flame | 600 mm |
| Kebab cooker and salamander | 200 mm |
Appendix E7.1, unless otherwise reduced, for example where fire suppression is fitted. Energy Safe Victoria has confirmed the equivalent gas clearance is measured on a radius, so filters beside the appliance count too.
Tall appliances are the easy case
Over rack ovens and combi ovens the emission point is the door or the top vent, often only half a metre below the hood, so the 1.2 m is easily met. The hard case is the opposite: a canopy hung at 2.5 m for tall equipment, then reused over 900 mm fryers. It has to come down, which is the single most common reason an inherited canopy cannot simply be reconnected. More on that in reusing an existing exhaust.
Overhang goes with height
Clause 3.5 bases the table on a minimum overhang beyond the cooking surface: 150 mm for process Types 1 to 4, 300 mm for Type 5, 600 mm for woks and 450 mm for bread and steam-producing combination ovens. The higher the hood sits, the wider the plume has spread by the time it gets there, so overhang and height are decided together.
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Send your equipment listQuestions
How high should a commercial kitchen canopy hang?
AS 1668.2-2012 Appendix E4 requires the lower edge to be at least 2 m above the floor at the operator side and no more than 1.2 m above the cooking appliance. Height multiplies the required airflow, because the prescriptive rate is Q = K x P x H with H measured from the appliance.
How far above the cooking surface do grease filters have to be?
Under AS 1668.2-2012 Appendix E7.1, unless otherwise reduced: 1350 mm over charcoal and similar open fires, 1050 mm over naked flame such as a gas stove, 600 mm over electric equipment or a fixed plate or pan above a gas flame, and 200 mm over kebab cookers and salamanders.
More memos
General guidance, not a design. Clause references are to AS 1668.2-2012 with Amendments 1 and 2 (called up by NCC 2022) and AS/NZS 5601.1:2022; NCC 2025 calls up AS 1668.2:2024, where numbering and some values differ, so confirm the edition with your building surveyor. I do the design and calculations as a mechanical engineer (MIEAust); the mechanical contractor installs, commissions and certifies, and a licensed gasfitter certifies gas work. More: kitchen exhaust and ventilation design in Perth · all design memos