Phoenix Journal · Extraction
A canopy only captures well when its height, overhang and airflow are right. Here is how to position one so grease, steam and heat are caught before they reach the room.
Kitchen extraction · Design & capture
A canopy only earns its keep when it sits in the right place - close enough and wide enough to catch the plume of grease, steam and heat before it rolls out into the room.
Get the geometry wrong and no amount of fan power will fix it. You end up with grease drifting onto walls and ceilings, condensation dripping back onto the range, and a kitchen that feels hot and greasy no matter how hard the system works. This guide walks through how to position a canopy for effective capture, using the dimensions and airflow figures set out in the recognised UK guidance so your extraction actually contains what it is meant to.
Capture is governed by three things - how high the canopy sits, how far it overhangs the appliances, and how fast air moves through it. The Building Engineering Services Association specification DW/172 and the European standard BS EN 16282 are the reference points UK designers work to, and the figures below come straight from that guidance.
Every appliance produces a different plume, and the canopy has to be positioned around the worst of them. A char grill throws a hot, buoyant column of grease-laden vapour that rises fast and needs a low, generous canopy directly over it. A bank of fryers gives off fine oil mist that spreads sideways as it cools, so side overhang matters as much as height. Combination ovens behave differently again - most of the time they sit quietly, then release a wall of steam the moment the door swings open, which is exactly why the guidance asks for that deeper 600 mm front overhang.
When you are positioning over a mixed cook line, work to the most demanding appliance rather than the average. It is tempting to centre a canopy neatly over a run of equipment and split the difference, but the plume does not compromise. If the grill sits at one end, the canopy needs to be low and wide enough there, even if that means it is more generous than strictly necessary over the lighter equipment beside it. Thinking about the highest, hottest, greasiest source first is the single most useful habit when you set the geometry.
It is easy to assume that lower is always better for capture, and within limits that is true - dropping the canopy shortens the distance the plume has to travel before it is caught, and it reduces the chance of cross draughts pulling contaminated air sideways. But go too low and you create problems of a different kind. Staff cannot work comfortably, the canopy gets in the way of tall stockpots and combi doors, and radiant heat from the range starts to cook the filters. That is why the 700 mm to 1200 mm band exists and why the 450 mm filter clearance is a hard limit rather than a suggestion. Position the canopy at the low end of the range where capture is critical, and only lift it where headroom or heat genuinely demand it.
Overhang is the forgiving part of the design. A plume rarely rises in a perfectly straight column - it wanders with door swings, passing staff, open windows and the pressure of the room. The overhang gives that wandering plume somewhere to go that is still under the canopy. Skimp on it and the edges of the plume escape, settling as a greasy film on the wall behind the range or the ceiling in front of it. That film is not just unsightly; it is a fire load and a hygiene problem, and it is the classic sign of a canopy that is either too small or badly centred. When in doubt, more overhang on the free sides is cheap insurance against escaped grease.
You can have the height, the overhang and the velocity exactly right and still watch smoke roll out into the room if the air balance is wrong. A canopy extracting hard from a sealed kitchen has nowhere to draw replacement air from, so it pulls against the building - dragging air down flues, whistling under doors, and losing the very capture velocity you designed for. Providing make-up air at around 85 to 90 per cent of the extract volume keeps the room close to neutral pressure, so the fan does the job it was sized for. Poor air balance is also a leading cause of condensation forming under the canopy, where warm, moist air is not carried away cleanly and instead cools and drips back down.
Some kitchens add filtration or odour treatment such as UV or ozone within the canopy or ductwork to break down grease and smells before discharge. These can be worthwhile, but they treat what the canopy has already captured - they do nothing for the plume that escaped past a badly placed edge. If you are weighing up whether UV and ozone canopy systems are worth it, get the positioning and air balance right first, because a well captured plume is what makes any downstream treatment effective rather than an expensive afterthought.
Finally, remember that positioning is only the start of the story. A canopy that captures well collects grease faster, which means the filters, plenum and ductwork behind it need cleaning on a sensible schedule to keep that capture performing and to keep you compliant with insurance and fire safety expectations. Good geometry and regular deep cleaning work together - one without the other rarely lasts.
Questions
Wall and island canopies are usually mounted between 700 mm and 1200 mm above the cooking surface, with the underside of the canopy sitting roughly 2000 mm to 2100 mm above the finished floor. Sitting towards the lower end of that band gives tighter capture. You must also keep at least 450 mm clearance from the cooking surface to the underside of the grease filters so radiant heat and flame cannot reach them.
As a baseline the canopy should exceed the footprint of the cooking line by at least 250 mm on each free side. Over a gas cook line, allow around 300 mm of overhang to the front and sides, and give combination or steaming ovens at least 600 mm at the front because steam surges forward when the door opens. Solid fuel appliances need the overhang extended beyond the door in its open position.
For medium and heavy duty ranges, aim for a capture velocity into the canopy face of around 0.5 m/s to 0.6 m/s or higher, in line with DW/172 and BS EN 16282. Just as important is achieving the correct face velocity across the baffle grease filters, as this is what delivers their high grease removal efficiency and fire protection. Too little velocity and the plume escapes; too much wastes energy and oversizes the fan.
In most cases the problem is geometry or air balance rather than fan power. If the canopy is too small, mounted too high, or badly centred over the cook line, the edges of the plume simply fall outside it. Equally, if the kitchen has no proper make-up air the fan pulls against the building and loses capture velocity. Providing replacement air at around 85 to 90 per cent of the extract volume usually restores performance.
Phoenix Duct Clean · by the numbers
The right kit only helps if the system stays clean. Phoenix degreases canopies, filters and ductwork to TR19 Grease - UK-wide, overnight.