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Kitchen extraction cleaning - canopy position
A canopy only extracts what it captures - and capture depends on getting the canopy right: covering the cooking with enough overhang, at the right height, and not fighting draughts or badly-placed make-up air. A poorly-positioned canopy lets the plume escape. Here is how to position a canopy for effective capture - and why a clean canopy is what keeps that capture working. This is general information; canopy design is for a competent designer.
The short answer
The canopy is the first stage of the extraction - and if it doesn't capture the cooking plume, nothing downstream can extract it. So how the canopy is positioned for capture is fundamental. Here is what makes capture effective. This is general information; the canopy sizing and positioning is a design matter for a competent designer. Capture: the canopy's job. When food cooks, it produces a rising plume of heat, smoke, steam and grease-laden vapour. The canopy's job is to capture that plume - to be positioned over the cooking so the rising plume enters the canopy and is drawn into the extraction. The canopy only extracts what it captures: any plume that escapes the canopy (spreading out into the kitchen instead of being caught) isn't extracted - so it lingers as heat, smoke and grease in the kitchen. So effective capture is the foundation of effective extraction. What makes capture effective. (1) Coverage and overhang. The canopy must be sized to cover the cooking appliances beneath it - and, importantly, to overhang them (extend beyond the appliances on the relevant sides). This is because the plume spreads outward as it rises, so a canopy only the size of the appliances would miss the spreading edges of the plume; the overhang catches the spreading plume. So proper coverage plus overhang is essential. (2) Height. The canopy should be at the right height above the cooking - within the design guidance. Too low and it obstructs the cooking or is impractical; too high and the plume spreads and cools too much before reaching the canopy, so it escapes the sides - weakening capture. So there's an optimal height range for capture. (3) An undisturbed capture zone. Capture happens in the zone between the cooking and the canopy - and it can be spoiled by air disturbance: cross-draughts (from doors, windows, fans, passing traffic) can blow the plume sideways out of the capture zone; and make-up air blown across the canopy face can push the plume out from under the canopy (which is why make-up air must be well-distributed, not aimed at the canopy). So the capture zone needs to be reasonably undisturbed. Positioned right vs wrong. A canopy sized to cover the appliances with proper overhang, at the right height, in an undisturbed zone, captures the plume effectively - so the extraction extracts it. A canopy too small, under-overhung, too high, or in a draughty/disrupted spot lets the plume escape - so the extraction can't extract what never got captured (a hot, smoky, greasy kitchen despite a running fan). The cleaning connection. Finally, a clean canopy and system are what keep the designed capture and airflow working: the capture depends on the extraction pulling its designed airflow through the canopy, and grease-choking (clogged filters, grease-laden ductwork, a strained fan) reduces that airflow - so even a well-positioned canopy captures less if the system is grease-choked. So keeping the extraction clean preserves the capture. So position a canopy for effective capture with proper coverage, overhang and height, in an undisturbed zone - and keep it clean so the capture keeps working. So capture depends on position and a clean system. This is general information; canopy design is for a competent designer.
Key points
Capture is the canopy's job
The fundamental point about a canopy is that its job is to capture the cooking plume - and it only extracts what it captures. When food cooks, it produces a rising plume of heat, smoke, steam and grease-laden vapour. The canopy, positioned over the cooking, is there to capture that plume - to catch the rising plume so it enters the canopy and is drawn into the extraction (through the filters, ductwork and fan, and out). So the canopy is the capture stage of the extraction.
The crucial consequence is that the canopy only extracts what it captures. Any part of the plume that escapes the canopy - spreading out into the kitchen instead of being caught - is not extracted; it lingers in the kitchen as heat, smoke and grease. So if the canopy doesn't capture the plume effectively, no amount of downstream extraction can extract it (the fan can only pull what the canopy caught). This makes effective capture the foundation of effective extraction - and effective capture depends on positioning the canopy right (coverage, overhang, height, an undisturbed zone), covered in the next sections. A poorly-positioned canopy is a fundamental failure, letting the plume escape at the very first stage. So capture is the canopy's job - it only extracts what it catches. So the canopy only extracts what it captures. This is general information.
Cover and overhang the cooking
The first requirement for effective capture is that the canopy covers the cooking appliances and overhangs them - because the plume spreads as it rises, so the canopy must be bigger than the appliances to catch it. The canopy must be sized to cover the cooking appliances beneath it (so the whole cooking line is under the canopy). But covering isn't enough on its own: it must also overhang the appliances - extend beyond them on the relevant sides. This is because the rising plume spreads outward as it rises (it doesn't go straight up), so by the time it reaches canopy height it's wider than the appliances.
A canopy only the size of the appliances would miss the spreading edges of the plume - letting them escape past the canopy's edges. The overhang catches this spreading plume: by extending beyond the appliances, the canopy covers where the plume has spread to at canopy height. So proper coverage plus overhang is essential to catching the whole plume. The right overhang is a design matter (depending on the appliances, the plume, the canopy type and height) - but the principle is that the canopy must be larger than the cooking line it serves, to catch the spreading plume. Too little overhang, and the plume escapes at the edges. So cover and overhang the cooking - catch the plume as it spreads. So proper overhang catches the spreading plume. This is general information; sizing is for a competent designer.
Get the height right
The second requirement is the right height - the canopy mounted at a height that captures the plume effectively, within the design guidance. Height matters because it affects capture. Too low, and the canopy obstructs the cooking or is impractical to work under (and may be a burn or clearance issue). Too high, and capture weakens: the higher the canopy above the cooking, the more the plume spreads and cools before reaching it - so a plume that's still rising and coherent at a sensible height will have spread wide and lost momentum if the canopy is too high, letting more of it escape the sides.
So there's an optimal height range - high enough to clear the appliances and be practical, but not so high that the plume disperses and escapes before reaching the canopy. This range is set by design guidance (depending on the canopy type, the cooking, and the overhang). Getting the height right, together with proper coverage and overhang, means the canopy is positioned in the right relationship to the plume to capture it. A canopy mounted too high - a common fault - undermines capture even if it's the right size, because the plume has spread beyond it by the time it arrives. So get the height right - not so high the plume escapes (nor so low it's impractical). So the height should be within the design guidance for capture. So position it at the right height for capture. This is general information; the height is a design matter for a competent designer.
Keep the capture zone undisturbed
The third requirement is an undisturbed capture zone - because the capture happens in the space between the cooking and the canopy, and air disturbance there can push the plume out of that zone. Cross-draughts: air currents across the capture zone - from open doors, windows, other fans, or people and traffic passing - can blow the rising plume sideways, out from under the canopy, before it's captured. So a canopy in a draughty spot (near a door, a window, a strong air current) can lose capture even if well-sized and positioned. Minimising cross-draughts in the capture zone helps capture.
Make-up air: importantly, the make-up air (the fresh replacement air) must be well-distributed, not blown across the canopy face - because make-up air aimed at or across the canopy can push the plume out from under it, spoiling capture (as covered in the make-up air design page). So the make-up air must be introduced away from the canopies, gently, so it replaces the extracted air without disturbing the capture. So keeping the capture zone reasonably undisturbed - free of cross-draughts and not disrupted by badly-placed make-up air - is essential to the capture working. Even a well-sized, well-positioned canopy can be defeated by air disturbance in its capture zone. So keep the capture zone undisturbed - draughts and make-up air spoil capture. So protect the capture zone from air disturbance. This is general information.
Keep it clean, keep it capturing
Finally, a well-positioned canopy captures effectively only while the system delivers its designed airflow - and keeping the extraction clean is what preserves that airflow, so a clean system keeps the capture working. Capture depends not just on the canopy's position but on the extraction pulling its designed airflow through the canopy (the airflow is what draws the captured plume in). If the system becomes grease-choked - clogged filters, grease-laden ductwork, a strained fan - the airflow drops, so even a well-positioned canopy captures less (it can't draw the plume in as strongly). So grease-choking undermines capture, regardless of good positioning.
So keeping the extraction clean (to TR19 Grease, at the right frequency) preserves the designed airflow, which preserves the capture - the well-positioned canopy keeps capturing effectively because the system keeps pulling its full airflow. This ties the design (position the canopy right) to the maintenance (keep it clean): both are needed for effective capture. A canopy positioned perfectly but served by a grease-choked system captures poorly; one positioned right and kept clean captures well. So keep it clean, keep it capturing - capture depends on airflow, and airflow on cleaning. So position the canopy for capture (coverage, overhang, height, an undisturbed zone) and keep the system clean to maintain the airflow that capture relies on. So a clean system keeps the capture working. This is general information; canopy design is for a competent designer.
Questions
It should cover the cooking appliances with enough overhang beyond them, at the right height, in a capture zone free of draughts and make-up-air disruption - so it catches the rising plume. The canopy captures the rising plume of heat, smoke and grease, and only extracts what it captures - so positioning is key. It must cover the cooking appliances and overhang them (extend beyond them), because the plume spreads as it rises, so the overhang catches the spreading edges. It should be at the right height (within design guidance) - not so high that the plume spreads and escapes before reaching it. And the capture zone should be undisturbed - free of cross-draughts (from doors, windows, fans) and not disrupted by make-up air blown across the canopy face. Positioned this way, the canopy captures the plume effectively. And keeping the system clean preserves the airflow the capture depends on. So cover and overhang the cooking, at the right height, in an undisturbed zone. So proper cover, overhang, height and an undisturbed zone. This is general information; design is for a competent designer.
Because the cooking plume spreads outward as it rises, so by canopy height it's wider than the appliances - a canopy only the size of the appliances would miss the spreading edges, which the overhang catches. The rising plume of heat and vapour from the cooking doesn't go straight up - it spreads outward as it rises. So by the time it reaches the canopy, it's wider than the appliances that produced it. A canopy sized only to match the appliances would therefore miss the spreading edges of the plume, letting them escape past the canopy's edges into the kitchen. The overhang - the canopy extending beyond the appliances on the relevant sides - catches this spreading plume, covering where it has spread to at canopy height. So the overhang is essential to capturing the whole plume, not just the part directly above the appliances. Too little overhang lets the plume escape at the edges. So it overhangs to catch the plume as it spreads. So because the plume spreads as it rises. This is general information.
Yes - if it's too high, the plume spreads and cools too much before reaching it, so more escapes the sides and capture weakens; there's an optimal height range within the design guidance. Height affects capture. A canopy mounted too high above the cooking captures poorly, because the higher it is, the more the plume spreads and loses momentum before reaching it - so a plume that would be captured at a sensible height has spread wide and dispersed by the time it reaches a too-high canopy, letting more escape the sides. (Too low is also a problem - obstructing the cooking or impractical.) So there's an optimal height range, set by design guidance for the canopy type and cooking. Mounting a canopy too high is a common fault that undermines capture even if the canopy is the right size. So yes - a canopy can be too high, weakening capture; the height should be within the design range. So yes - too high weakens capture. This is general information; the height is a design matter.
Cross-draughts in the capture zone - from doors, windows, fans or traffic - can blow the rising plume sideways out from under the canopy before it's captured, so a draughty location weakens capture even with a well-sized canopy. Capture happens in the space between the cooking and the canopy, and air disturbance there can push the plume out of that zone. Cross-draughts - air currents from open doors, windows, other fans, or people and traffic passing near the cooking - can blow the rising plume sideways, out from under the canopy, before it's drawn in. So a canopy positioned in a draughty spot (near a door or strong air current) can lose capture even if it's well-sized and at the right height. Minimising cross-draughts in the capture zone (siting the cooking away from strong draughts, managing door and window air) helps preserve capture. So draughts spoil capture by blowing the plume out of the capture zone. So they blow the plume out from under the canopy. This is general information.
Yes - make-up air blown across the canopy face can push the plume out from under the canopy, spoiling capture; so make-up air must be well-distributed, introduced away from the canopies, not aimed at them. Make-up air (the fresh replacement air for what the extraction removes) is essential, but it must be introduced carefully. If it's blown across or at the canopy face, it can disturb the capture - pushing the rising plume sideways, out from under the canopy, before it's caught (spoiling exactly the capture the canopy is meant to achieve). So make-up air must be well-distributed: introduced away from the canopies, at gentle velocities, so it replaces the extracted air without disturbing the capture zone (as covered in the make-up air design page). Badly-placed make-up air is a common cause of poor capture despite a well-positioned canopy. So yes - make-up air can interfere, which is why it must be distributed away from the canopy. So yes - if blown across the canopy face. This is general information.
Yes indirectly - capture depends on the system pulling its designed airflow through the canopy, and grease-choking (clogged filters, grease-laden ductwork, a strained fan) reduces that airflow, so a grease-choked system captures less even with a well-positioned canopy. Capture isn't just about the canopy's position - it depends on the extraction pulling its designed airflow through the canopy (the airflow draws the captured plume in). So if the system becomes grease-choked - clogged filters, grease-laden ductwork, a strained fan - the airflow drops, and even a well-positioned canopy captures less (it can't draw the plume in as strongly). So keeping the extraction clean (to TR19 Grease, at the right frequency) preserves the designed airflow, which preserves the capture. A canopy positioned perfectly but served by a grease-choked system captures poorly. So keeping the canopy and system clean is part of keeping the capture working - the position sets it up, the cleaning maintains it. So yes - a clean system keeps the airflow that capture needs. This is general information.
A well-positioned canopy captures the plume, but only while the system pulls its designed airflow - and grease chokes that. We keep the whole system clean to TR19 Grease so the airflow, and the capture, keep working as designed. Ask us to keep your extraction clean and capturing. This is general information; canopy design is for a competent designer.
