Phoenix Journal · Extraction
In an open-plan or theatre kitchen the extraction canopy is part of the dining room, which means a build-up that used to hide in the ductwork is now a guest-facing problem as much as a fire risk.
Case notes
A busy chef’s-table restaurant put its grill line on full display - polished canopy, brass trim, the works - and for eighteen months nobody cleaned above the filters.
The room was designed to sell the theatre of cooking. Diners sat close enough to feel the heat off the chargrill, watch the pass, and breathe the same air the extraction was pulling. It looked immaculate. The stainless steel canopy was wiped down every night, the baffle filters were swapped and run through the dishwasher, and the front of house team were rightly proud of how clean it all read from the tables.
What nobody could see was the ductwork. Above the plenum, in the horizontal run heading for the roof, grease had been quietly laminating onto the duct walls with every service. Because the visible parts were spotless, the assumption was that the whole system was fine. Then two things happened in the same fortnight. A guest sitting nearest the pass complained twice about a stale, fatty smell that seemed to drift out whenever the grill was flat out. And the building’s insurer, mid-renewal, asked for a current extract cleaning certificate to TR19 Grease. There wasn’t one. The last “clean” had been the filters and the canopy face, nothing more.
When a specialist finally opened the system up, the deposit thickness readings in the first horizontal section came back well over 500 microns in places - more than double the level at which a clean is due, and firmly into spot-clean-immediately territory. In a concealed kitchen that’s a serious fire risk. In a theatre kitchen it was also, quietly, a customer-experience problem that had been building for months.
Nothing here was laziness. The kitchen was clean by every measure the team could actually see. The failure was in mistaking the visible surfaces for the system, and that mistake is far easier to make in an open-plan or theatre layout precisely because the visible surfaces are so prominent.
Three things stacked up:
The insurer’s request was the sharp end of it. TR19 Grease, published by BESA, is not a law in itself, but it is referenced so consistently in commercial leases, fire risk assessments and insurance policies that a missing certificate can put a renewal - or a post-incident claim - in real jeopardy. Around 70% of commercial kitchen fires are linked to extract systems and the grease inside them, which is why underwriters care so much about the paperwork.
The numbers that matter
Those figures are the spine of TR19 Grease. A clean becomes due when the mean deposit across the ductwork reaches roughly 200 microns; anywhere reading 500 microns or more needs immediate attention, not a diary note. After cleaning, the system should measure under 50 microns as an average, and that has to be evidenced rather than asserted. In our case-notes kitchen, the readings had been left to climb unseen because nobody was measuring at all.
Putting this right - and keeping it right - is not complicated, but it does mean treating the extract system as one continuous run from the canopy to the roof discharge, not as a set of surfaces the diners happen to see. Here is the order we’d work through it.
There is a quiet upside to extraction being on show. Because the canopy and the room share air and sightlines, problems announce themselves earlier - a smell at the pass, a haze over the grill, a filter that greys faster than it used to. Treated as signals rather than nuisances, they let you catch a system before it drifts past 200 microns. It also concentrates the mind on odour control: a theatre kitchen usually needs its carbon or molecular filtration genuinely maintained, not just installed, because guests will notice the day it stops working. And because on-show kitchens tend to run their extraction hard and long, they are worth watching on running cost too - if you like to see how your site compares, it can help to benchmark your kitchen’s energy use against peers so a fan running flat out to shift stubborn air doesn’t quietly cost you twice.
The lesson from the case notes is simple. A theatre kitchen is designed so people look at it, and that is exactly why it is tempting to clean only what they look at. The grease that matters most for fire, for smell and for your insurance is the grease nobody in the dining room can see - and the only way to know it is under control is to open the system up, measure it, and keep the certificate to prove it.
Questions
No. Wiping the canopy face and washing the baffle filters is daily housekeeping, and it only deals with the very first part of the system. TR19 Grease covers the whole extract route from the canopy through the plenum, ductwork and fan to the discharge point, and compliance means the full run is cleaned back to under 50 microns and certified. In an open-plan kitchen it is easy to assume the spotless visible surfaces mean the concealed ductwork is clean too, but they are separate things.
It depends on how hard the kitchen works rather than how it looks. As a guide, heavy use of around 12 to 16 hours a day points to a three-monthly clean, moderate use of 6 to 12 hours to six-monthly, and lighter use to annually. Theatre kitchens usually feature chargrilling and heavy searing that load a system quickly, so most sit at the heavy end and need the more frequent schedule regardless of cover numbers.
Because the dining room shares air with the cooking line, any weakness in the extract system reaches your guests directly. A stale, fatty note when the grill is flat out usually means grease has built up in the ductwork or the odour-control media has loaded up and needs servicing. It is often the first sign a system is overdue a proper clean, arriving before any deposit test would - so it is worth treating as a prompt to survey the whole run rather than just re-wiping the canopy.
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.