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Extraction cleaning - two kinds of fire
Not all kitchen fires are the same. A grease fire on the cooking line and a fire inside the ductwork are different events - starting in different places, behaving differently, and prevented in different ways. Telling them apart matters, because controlling each fully means understanding what it is and what stops it. Both are grease-related, but they are not the same risk.
The short answer
A grease fire and a duct fire are different kinds of kitchen fire. A grease fire typically starts on the cooking line - hot fat or oil igniting on or around the cooking equipment - a fast, fierce fire at the point of cooking, guarded against by safe cooking practice and the automatic suppression system over the cooking line. A duct fire starts or spreads inside the extraction ductwork, where accumulated grease lining the ducts ignites and burns along them, spreading fire through the building via the duct route - prevented chiefly by keeping the ductwork clean of grease. So the two differ in where they occur, how they behave, and how they are prevented. Both stem from grease, but controlling each fully means addressing its own location and prevention.
Not all kitchen fires are the same
It is easy to lump kitchen fires together as one hazard, but there are meaningfully different kinds, and two in particular are worth distinguishing: the grease fire on the cooking line, and the fire inside the ductwork. These are different events - they start in different places, behave in different ways, and are prevented by different means. Treating them as one risk obscures the fact that fully controlling kitchen fire risk means addressing both, each in its own way. So understanding the difference between a grease fire and a duct fire is understanding that the kitchen has more than one fire risk, needing more than one line of defence.
Both are related to grease - grease is central to the kitchen fire risk in general - but they involve grease differently and occur in different parts of the system. The grease fire is at the cooking, where fat and oil are hot; the duct fire is in the extraction, where grease has accumulated. So while grease connects them, they are distinct in location and character, and prevented differently. Telling them apart matters precisely because their prevention differs: what guards against a grease fire on the cooking line is not the same as what prevents a fire in the ductwork, so controlling both requires understanding each. This distinction is the basis for a complete approach to kitchen fire safety.
The grease fire
A grease fire, in this sense, is a fire on the cooking line - the ignition of hot fat or oil on or around the cooking equipment. Cooking involves hot fats and oils, and these can ignite: an overheated pan of oil, fat catching from a burner, a spill igniting - the fierce, fast fire that erupts at the point of cooking. This is the classic kitchen fire that a busy cooking operation is prone to, occurring right where the cooking happens, and it can be dangerous and spread quickly if not controlled immediately. So the grease fire is a fire at the cooking equipment, involving the hot fats and oils of cooking.
Its prevention is focused on the cooking line. Safe cooking practice - not overheating oil, managing fats carefully, not leaving cooking unattended - reduces the likelihood of ignition. And the automatic fire suppression system over the cooking line is the key protection: it is designed precisely to detect and put out a fire on the cooking equipment, discharging suppressant onto the fire the moment one starts. So the grease fire on the cooking line is guarded against by safe practice and the suppression system aimed at the cooking equipment - the defences appropriate to a fire at the point of cooking. This is a different set of preventions from what protects against a duct fire, because the grease fire is a different event in a different place.
The duct fire
A duct fire is a different event: a fire that starts or spreads inside the extraction ductwork, where accumulated grease lining the ducts ignites and burns. Over time, the extraction ductwork accumulates grease from the grease-laden air passing through it, coating the inside of the ducts. This grease is combustible, so if it ignites - perhaps from a grease fire on the cooking line reaching the ductwork, or from another ignition source - it can burn along the inside of the ducts, fed by the grease lining them. So the duct fire is a fire within the ductwork itself, fuelled by the accumulated grease coating the ducts.
The particular danger of a duct fire is that it can spread fire through the building via the ductwork. The ducts run through the building, connecting spaces, so a fire burning along the grease-lined ductwork can travel through the building, carrying fire far from where it started and potentially into other areas. This makes a duct fire a serious building fire risk, distinct from the grease fire contained at the cooking line. And its prevention is different too: the chief defence against a duct fire is keeping the ductwork clean of grease, removing the fuel that would let a fire burn along the ducts. A clean duct has little for a fire to feed on; a grease-lined one is a fire path lined with fuel. So the duct fire is prevented primarily by cleaning the ductwork - a quite different prevention from the safe practice and suppression that guard the cooking line.
Why the distinction matters
The distinction between the two fires matters because controlling kitchen fire risk fully means addressing both, each with its own prevention. The grease fire on the cooking line is guarded against by safe cooking practice and the suppression system; the duct fire is prevented chiefly by keeping the ductwork clean. These are different measures for different fires, and neither substitutes for the other: a suppression system over the cooking line does not clean the grease from the ducts, and clean ducts do not put out a fire on the cooking equipment. So a complete approach needs both - the cooking-line defences and the clean ductwork - because the two fires are different risks needing different prevention.
This is why understanding the difference is practically important. A kitchen focused only on the cooking-line fire - the suppression system and safe practice - might neglect the ductwork, leaving a duct fire risk from accumulated grease unaddressed. A kitchen focused only on cleaning the ducts might overlook the cooking-line protection. Fully controlling the fire risk means recognising both kinds of fire and providing for each: safe practice and suppression for the grease fire on the cooking line, and regular ductwork cleaning for the duct fire in the extraction. Both stem from grease, but they are different events in different places, prevented differently - so telling them apart, and addressing each, is what makes for complete kitchen fire safety. The two risks together are the fuller picture, and both need their own line of defence.
The takeaway
A grease fire and a duct fire are different kinds of kitchen fire. A grease fire starts on the cooking line - hot fat or oil igniting on or around the cooking equipment, a fast, fierce fire at the point of cooking - guarded against by safe cooking practice and the automatic suppression system aimed at the cooking line. A duct fire starts or spreads inside the extraction ductwork, where accumulated grease lining the ducts ignites and burns along them, potentially spreading fire through the building via the duct route - prevented chiefly by keeping the ductwork clean of grease.
So the two differ in where they occur, how they behave, and how they are prevented - and neither prevention substitutes for the other. Controlling kitchen fire risk fully means addressing both: safe practice and suppression for the grease fire on the cooking line, and regular ductwork cleaning for the duct fire in the extraction. A kitchen that provides for one but neglects the other leaves a real fire risk unaddressed. Both stem from grease, but they are different events in different places needing different defences - so telling them apart, and guarding against each, is what makes for complete kitchen fire safety.
Questions
A grease fire starts on the cooking line - hot fat or oil igniting on or around the cooking equipment, a fast fire at the point of cooking. A duct fire starts or spreads inside the extraction ductwork, where accumulated grease lining the ducts ignites and burns along them. Different location, behaviour and prevention.
A fire on the cooking line - the ignition of hot fat or oil on or around the cooking equipment, such as an overheated pan of oil or fat catching from a burner. It is the fierce, fast fire that erupts at the point of cooking, which a busy cooking operation is prone to, and can spread quickly if not controlled immediately.
By safe cooking practice - not overheating oil, managing fats carefully, not leaving cooking unattended - and by the automatic fire suppression system over the cooking line, which is designed to detect and put out a fire on the cooking equipment. These are the defences appropriate to a fire at the point of cooking.
A fire that starts or spreads inside the extraction ductwork, where accumulated grease lining the ducts ignites and burns along them. The particular danger is that it can spread fire through the building via the ductwork, which runs through the building connecting spaces - carrying fire far from where it started.
Chiefly by keeping the ductwork clean of grease - removing the fuel that would let a fire burn along the ducts. A clean duct has little for a fire to feed on; a grease-lined one is a fire path lined with fuel. So regular ductwork cleaning is the key defence against a duct fire, quite different from the cooking-line protections.
Because controlling kitchen fire risk fully means addressing both, each with its own prevention - and neither substitutes for the other. A suppression system does not clean the ducts, and clean ducts do not put out a cooking-line fire. A kitchen that provides for one but neglects the other leaves a real fire risk unaddressed.
The duct fire - grease igniting inside the ductwork and spreading through the building - is prevented chiefly by keeping the ducts clean, which is exactly what our extraction cleaning does.
