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Kitchen extraction cleaning - smoke
Smoke filling the kitchen during service - drifting out past the canopy instead of being drawn away - means the extraction isn't capturing it as it should. Usually that means a greasy, choked system pulling too little air, or a make-up air problem starving the extraction. Here is why smoke escapes into the kitchen during service, and what to do about it. This is general guidance.
The short answer
Smoke filling the kitchen during service is more than unpleasant - it's a sign the extraction is failing at its core job of capturing and removing the cooking smoke. It also means poor air quality for the staff and, often, an underlying problem worth fixing. Here's why the smoke is escaping and what to do. This is general guidance. The extraction should capture the smoke. The extraction's core job is to capture and remove the smoke (along with the heat, steam and grease) the cooking produces: the canopy captures the rising plume over the appliances, and the system draws it up the ductwork and away. So a well-functioning extraction captures the smoke at the canopy and takes it out of the kitchen, keeping the air clear. Smoke escaping means capture is failing. So if smoke is filling the kitchen during service - drifting out past the canopy edges into the kitchen instead of being drawn away - it means the extraction isn't capturing it as it should. The capture at the canopy is failing: the smoke rising off the cooking isn't being fully drawn into the canopy and away, so it escapes into the kitchen. So the smoke in the kitchen is a sign of failing capture - the extraction not doing its core job. Why during service? Because service is when the cooking (and the smoke) is heaviest - so a weak extraction is most likely to be overwhelmed then. During a busy service, with lots of cooking producing lots of smoke, an extraction that's underperforming (capturing weakly) can't keep up, so the smoke escapes. (At quieter times, with less smoke, the weak extraction might just cope.) So the smoke filling the kitchen 'during service' points to an extraction that can't handle the peak smoke load - i.e. one that's underperforming. Reason 1: a greasy, choked system. The commonest reason the extraction is underperforming is that it's greasy. Grease build-up (in the filters, ductwork and on the fan) chokes the airflow, so the system moves less air and the capture at the canopy weakens - so smoke escapes rather than being drawn away (as covered in the reduced-suction-at-the-canopy and airflow-dropping-off pages). This is the same choked-airflow problem behind a hotter, humid kitchen - here showing up as escaping smoke. So a greasy, grease-choked system is the first thing to suspect. Reason 2: a make-up air problem. The other common reason is a make-up air problem. The extraction needs enough replacement (make-up) air coming into the kitchen to pull properly - you can only extract as much air as you can replace. So if the make-up air is inadequate (a failed supply fan, doors or windows that used to be open now shut, a tightened-up building), the extraction is starved and pulls less air - so capture weakens and smoke escapes, even if the system itself is clean (as covered in the role-of-make-up-air page). Other possibilities. Other causes of poor capture include a canopy that's too small or badly positioned to capture the plume (a design issue), or a failing fan (not moving enough air). So while grease and make-up air are the common causes, the canopy design or fan may be involved. What to do. So the approach: If the system is greasy or overdue a clean, clean it. A proper extraction clean removes the grease choking the airflow, restoring the capture at the canopy so the smoke is drawn away again - the readily fixable, commonest cause, and the first thing to address. If it's clean but smoke still escapes, look at the make-up air and canopy/fan. If a clean, well-performing extraction still can't capture the smoke, the make-up air may be inadequate (starving the extraction) or the canopy/fan may be undersized or badly positioned - matters for a ventilation specialist to assess. So the smoke problem is usually the extraction not pulling enough air - most often grease (clean it), sometimes make-up air (a specialist). The takeaway. So smoke filling the kitchen during service means the extraction isn't capturing it - usually because it's greasy and choked (pulling too little air), or starved of make-up air. Clean the extraction to restore the capture; if that doesn't resolve it, check the make-up air, canopy and fan. So clean the system to restore the smoke capture. This is general guidance.
Key points
Capture is failing
The extraction's core job is to capture and remove the smoke (along with the heat, steam and grease) the cooking produces: the canopy captures the rising plume over the appliances, and the system draws it up the ductwork and away. So a well-functioning extraction captures the smoke at the canopy and takes it out of the kitchen, keeping the air clear.
So if smoke is filling the kitchen during service - drifting out past the canopy edges into the kitchen instead of being drawn away - it means the extraction isn't capturing it as it should. The capture at the canopy is failing: the smoke rising off the cooking isn't being fully drawn into the canopy and away, so it escapes into the kitchen. So the smoke in the kitchen is a direct sign of failing capture - the extraction not doing its core job. This matters both for the immediate problem (a smoky kitchen, poor air quality for staff) and as a symptom of an underlying issue (usually the extraction underperforming). So capture is failing - smoke escaping means weak extraction - is the diagnosis: the smoke tells you the extraction isn't capturing it, which has a cause to find (covered next). So escaping smoke signals failing capture. This is general guidance.
Why during service
The smoke filling the kitchen 'during service' is a clue: service is when the cooking, and therefore the smoke, is heaviest - so a weak extraction is most likely to be overwhelmed then. During a busy service, with lots of cooking producing lots of smoke, an extraction that's underperforming (capturing weakly) can't keep up with the peak smoke load, so the smoke escapes into the kitchen.
At quieter times, with less cooking and less smoke, the same weak extraction might just about cope (capturing the smaller amount of smoke), so the problem may not show. But when service ramps up and the smoke load peaks, the weak extraction is overwhelmed and the smoke escapes. So the fact that it happens during service points to an extraction that can't handle the peak load - i.e. one that's underperforming (not moving enough air to capture the heavy service smoke). This is a useful clue: it confirms the extraction is under-capacity relative to the cooking, which points to it being choked (greasy) or starved (make-up air) rather than fine. So why during service - the smoke load is heaviest then - explains the timing: the weak extraction shows its inadequacy at the peak smoke load. The causes of that weakness are covered next. So service is when a weak extraction gets overwhelmed. This is general guidance.
Usually a greasy system
The commonest reason the extraction is underperforming (capturing weakly) is that it's greasy. Grease build-up (in the filters, ductwork and on the fan) chokes the airflow, so the system moves less air - and with less airflow, the capture at the canopy weakens, so smoke escapes rather than being drawn away (as covered in the reduced-suction-at-the-canopy and airflow-dropping-off pages). So a greasy, grease-choked system captures smoke poorly, letting it escape during service.
This is the same choked-airflow problem behind a greasy system's reduced heat removal (a hotter kitchen) and reduced moisture removal (a humid kitchen) - here it shows up as escaping smoke (failed capture). The grease reduces the airflow, and the reduced airflow can't capture the smoke. So a greasy system is the first thing to suspect when smoke fills the kitchen during service - especially if it's overdue a clean or shows other signs of being greasy (weak suction, a hotter or humider kitchen, a louder fan). And it's the readily fixable cause: cleaning the system restores the airflow and the capture. So usually a greasy system - grease chokes the airflow and capture - is the main cause: the grease reducing the airflow that captures the smoke. Cleaning is the fix (covered later). So suspect a grease-choked system first. This is general guidance.
Or a make-up air problem
The other common reason is a make-up air problem. The extraction needs enough replacement (make-up) air coming into the kitchen to pull properly - you can only extract as much air as you can replace. So if the make-up air is inadequate (a failed supply/make-up air fan, doors or windows that used to be open now shut, a tightened-up building reducing the incidental air), the extraction is starved and pulls less air - so the capture weakens and smoke escapes, even if the system itself is clean.
So a clean extraction can still let smoke escape if it's starved of make-up air - the kitchen goes into negative pressure and the extraction can't pull air it can't replace, so its capture drops (as covered in the role-of-make-up-air and airflow-balance pages). This is a ventilation issue rather than a cleaning one, and a common, under-appreciated cause of poor capture. So if the system is clean but smoke still escapes during service, the make-up air may be the problem - especially if the capture worsened after a change (a supply fan failing, doors being closed). Other possibilities include a canopy too small or badly positioned to capture the plume (a design issue), or a failing fan. So or a make-up air problem - a starved extraction can't capture - is the second common cause: the extraction, even clean, can't capture the smoke if it's starved of make-up air. So consider the make-up air, especially if the system is clean. This is general guidance.
What to do
So the approach to smoke filling the kitchen during service: first, if the system is greasy or overdue a clean, clean it. A proper extraction clean removes the grease choking the airflow, restoring the capture at the canopy so the smoke is drawn away again - the readily fixable, commonest cause, and the first thing to address. In many cases, cleaning restores the capture and the smoke problem resolves.
Then, if it's clean but smoke still escapes, look at the make-up air and the canopy/fan. If a clean, well-performing extraction still can't capture the smoke, the make-up air may be inadequate (starving the extraction), or the canopy may be undersized or badly positioned, or the fan failing - matters for a ventilation specialist to assess and address. And the smoke problem shouldn't be left, because beyond the discomfort it means poor air quality for the staff (breathing the smoke) and signals an underperforming extraction (often grease-laden, a fire and performance concern). So the sequence: clean the extraction (the common, cleanable cause), and if that doesn't resolve it, investigate the make-up air, canopy and fan (a specialist matter). So what to do - clean it, then check the make-up air - is the practical response: clean the system first (usually the fix), then look at the make-up air and canopy/fan if smoke still escapes. So clean the extraction, then check the make-up air and canopy. This is general guidance.
Questions
Because the extraction isn't capturing it - usually a greasy, choked system pulling too little air, or a make-up air problem starving it; service is when the smoke load peaks, so a weak extraction gets overwhelmed then. Smoke filling the kitchen during service means the extraction isn't capturing it as it should - the smoke drifting out past the canopy instead of being drawn away. The capture at the canopy is failing. It shows up 'during service' because that's when the cooking, and the smoke, is heaviest, so a weak extraction is most likely to be overwhelmed then. The commonest reason the extraction is weak is that it's greasy: grease build-up chokes the airflow, so the system moves less air and the capture weakens, letting smoke escape. Another common reason is a make-up air problem: the extraction needs enough replacement air to pull properly, so if the make-up air is inadequate, it's starved and captures weakly even when clean. Other causes: an undersized or badly-positioned canopy, or a failing fan. The fix: clean the extraction (the common, cleanable cause), and check the make-up air if it stays weak. So the extraction isn't pulling enough air - usually grease or make-up air. So failing capture, usually from grease. This is general guidance.
Yes - grease chokes the airflow, so a greasy system moves less air and the capture at the canopy weakens, letting smoke escape instead of being drawn away; it's the same choked-airflow problem behind a hotter, humid kitchen. Yes - a greasy extraction lets smoke escape. The extraction captures smoke by drawing the rising plume into the canopy and away, and how well it captures depends on how much air it moves. A greasy system moves less air, because grease build-up (in the filters, ductwork and on the fan) chokes the airflow - narrowing the path and loading the fan. So the capture at the canopy weakens, and the smoke escapes past the canopy into the kitchen rather than being drawn away. This is the same choked-airflow problem that makes a greasy system remove less heat (a hotter kitchen) and less steam (a humid kitchen) - here it shows up as escaping smoke (failed capture). So a greasy, grease-choked system is the commonest cause of smoke filling the kitchen. And it's the readily fixable cause: cleaning the system restores the airflow and the capture, so the smoke is drawn away again. So yes - a greasy system captures smoke poorly. So yes; suspect grease first. This is general guidance.
Because service is when the cooking and smoke are heaviest, so a weak, underperforming extraction can't keep up with the peak smoke load and gets overwhelmed - while at quieter times, with less smoke, it might just cope. The smoke escapes during service specifically because that's when the smoke load is heaviest. During a busy service, lots of cooking produces lots of smoke - so an extraction that's underperforming (capturing weakly, e.g. because it's greasy or starved of make-up air) can't keep up with the peak smoke load and gets overwhelmed, letting the smoke escape into the kitchen. At quieter times, with less cooking and less smoke, the same weak extraction might just about cope (capturing the smaller amount), so the problem may not show. So the timing - during service - is a clue that the extraction is under-capacity relative to the cooking: it manages when the load is light but fails when it peaks. This confirms the extraction is underperforming (choked by grease or starved of make-up air) rather than fine. So the smoke escapes at the peak load because the weak extraction can't handle it. So because the smoke load peaks and overwhelms a weak system. So service is the peak load a weak system fails at. This is general guidance.
If the cause is a greasy, choked system, yes - cleaning restores the airflow and the capture, so the smoke is drawn away; but if it's clean and smoke still escapes, the make-up air, canopy or fan may be the issue, needing a specialist. If the smoke is escaping because the extraction is greasy and choked (the commonest cause), then yes - cleaning it will stop the smoke escaping. A proper extraction clean removes the grease choking the airflow (in the filters, ductwork and fan), so the system moves more air and the capture at the canopy is restored - drawing the smoke away again instead of letting it escape. So cleaning is the readily fixable cause and the first thing to address, especially if the system is greasy or overdue a clean. However, if the extraction is already clean and well-performing but smoke still escapes, cleaning won't be the answer - the cause is likely a make-up air problem (the extraction starved of replacement air), or the canopy being undersized or badly positioned, or the fan failing. Those need a ventilation specialist to assess. So cleaning stops the smoke escaping if grease was the cause; if the system's clean and smoke still escapes, look at the make-up air, canopy and fan. So yes if it's greasy; otherwise check make-up air/canopy. This is general guidance.
Yes - staff breathing cooking smoke and particulates is poor for the working air quality, so smoke filling the kitchen is worth fixing for the staff's sake as well as comfort; a well-performing extraction keeps the air clear. Yes - smoke filling the kitchen is a concern for the staff's working environment. When the extraction fails to capture the smoke, the staff are left breathing the cooking smoke and grease particulates in the air, along with the heat and fumes - which is poor for the air quality they work in. So smoke in the kitchen isn't just uncomfortable and unpleasant; it means the staff are exposed to the smoke and particulates the extraction should be removing. So fixing the smoke problem matters for the staff's sake (their air, comfort and wellbeing), not just for the kitchen environment generally. A well-performing extraction captures and removes the smoke, keeping the air the staff breathe clear - which is part of what the extraction is for (protecting the air quality). Specific occupational air-quality matters are for the relevant assessment, but the general point is clear: restoring the extraction's capture (usually by cleaning) improves the air the staff breathe. So yes - it's worth fixing for the staff's air quality. So yes; the staff breathe the escaping smoke. This is general guidance.
Then the cause is likely the make-up air (the extraction starved of replacement air), the canopy (undersized or badly positioned), or a failing fan - matters for a ventilation specialist to assess and address. If smoke still escapes after the extraction is cleaned and performing well, the cause is probably not grease but something else. The likely candidates: a make-up air problem (the extraction starved of replacement air, so it can't pull properly even when clean - especially if the capture worsened after a supply fan failed or doors were closed); a canopy issue (the canopy too small or badly positioned to capture the plume - a design matter); or a failing fan (not moving enough air despite being cleaned). These are ventilation and design matters, so they need a ventilation specialist to assess and address (improving the make-up air, or correcting the canopy or fan). So after cleaning, if smoke still escapes, get a ventilation specialist to look at the make-up air, the canopy design and the fan. Don't leave the smoke problem - it means poor air quality and an underperforming extraction. So investigate the make-up air, canopy and fan with a specialist. So look at the make-up air, canopy and fan. This is general guidance.
Smoke escaping during service usually means a greasy, choked extraction capturing poorly; we clean the whole system to TR19 Grease, restoring the airflow and the capture at the canopy - so the smoke is drawn away, not left to fill the kitchen. Ask us to clean your extraction and restore its capture. This is general guidance.
