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Duct cleaning - gas safety
In a gas kitchen, the extraction and the gas safety are linked by a single device that makes sure they cannot come apart: the gas interlock. It ties the gas supply to the ventilation, so gas cannot flow to the appliances unless the extraction is running and proven to be working. Here is how a gas interlock works, and how it connects extraction and gas safety into one system.
The short answer
A gas interlock is a safety device that connects a kitchen's gas supply to its ventilation, so the two cannot be dangerously mismatched. It works on a simple principle: gas is only allowed to flow to the cooking appliances while the ventilation - the extraction and make-up air - is running and proven to be working. When the ventilation is running, the interlock permits the gas; if the ventilation is not running, or fails, the interlock isolates the gas, so the appliances cannot burn. The 'proven' part is key: the interlock does not just assume the fan is on, but verifies it - typically with an air-proving device (a pressure or airflow switch, or current-sensing on the fan) that confirms the extraction is actually running, not just switched on. So the interlock genuinely links extraction and gas safety: gas appliances can only operate when there is proven extraction to remove their combustion products and supply combustion air. This prevents the dangerous situation of gas burning without ventilation - which risks carbon monoxide build-up - by making working extraction a precondition for the gas. It is now the minimum standard for new commercial kitchen gas installations, because it directly ties the gas safety to the ventilation working.
Why gas and ventilation must be linked
The reason a gas interlock exists is that gas appliances burning without adequate ventilation is dangerous - so the gas and the ventilation need to be linked to prevent that combination. Gas appliances need ventilation for two related reasons: to supply the fresh air for clean combustion, and to remove the products of combustion. If gas appliances burn while the extraction is not running - not supplying combustion air or removing the products - combustion can suffer and, critically, carbon monoxide (the poisonous product of incomplete combustion) can build up in the kitchen, along with the heat and other combustion products. So gas burning without working extraction is exactly the situation that risks a dangerous, potentially deadly build-up of carbon monoxide.
Without a link between the gas and the ventilation, this dangerous mismatch could easily happen - the appliances left on with the extraction off, or the extraction failing while the appliances keep burning. Relying on people to always ensure the extraction is running whenever the gas is on is unreliable, and gives no protection if the extraction fails unnoticed. So there is a real need to link the gas and the ventilation, so that gas cannot flow without the extraction running - which is exactly what the gas interlock does. It removes the reliance on people and the possibility of the mismatch, by making the gas depend on the ventilation. Understanding this danger - gas without extraction risking carbon monoxide build-up - is understanding why the interlock is needed: it exists to make sure that dangerous combination cannot occur.
How the interlock works
The gas interlock works by making the flow of gas to the appliances conditional on the ventilation running - a direct, automatic link. In practice, the interlock controls the gas supply through a gas valve, and it opens that valve (allowing gas to the appliances) only when the ventilation is running and proven, and closes it (isolating the gas) when the ventilation is not. So the sequence is: to use the gas appliances, the ventilation must be running; the interlock confirms it is; and only then does it allow the gas. If the ventilation stops or fails, the interlock closes the gas valve, cutting the gas so the appliances cannot burn without ventilation. So the gas literally cannot flow unless the extraction is running.
This makes working ventilation a precondition for the gas - the gas depends on the ventilation, automatically and continuously. The user cannot run the gas appliances without the ventilation, because the interlock will not allow the gas without it; and if the ventilation fails while the appliances are in use, the interlock cuts the gas, stopping the appliances. So the interlock enforces, automatically, that gas is only ever burning when there is ventilation to handle it - removing both the possibility of running the gas without the extraction, and the danger of the extraction failing unnoticed while the gas burns. This is the core of how the interlock connects extraction and gas safety: it makes the gas physically dependent on the proven running of the extraction, so the two cannot come apart. The link is not advisory but enforced by the device controlling the gas.
Proving the ventilation is running
A crucial subtlety is that the interlock does not just check whether the ventilation is switched on, but proves that it is actually running and moving air - because a fan switched on but not actually working (a failed motor, a broken belt, a blockage) would leave the gas flowing without real ventilation. So the interlock uses an air-proving device to verify the extraction is genuinely running. This is typically a pressure or airflow switch in the ductwork that detects the air actually moving, or a current-sensing device on the fan that detects it actually drawing power and running - either way, confirming the fan is not just powered but working and moving air. Only when this proving confirms real ventilation does the interlock allow the gas.
This proving is what makes the interlock genuinely safe rather than merely nominal. Checking only that the fan switch is on would give false assurance - the fan could be switched on but failed, leaving gas burning without ventilation while the interlock thought all was well. By proving the actual airflow or fan operation, the interlock ensures the gas is only allowed when there is real, working extraction - so a fan failure, not just a fan being switched off, cuts the gas. So the air-proving is the part that makes the interlock's link real: it ties the gas to the extraction actually working, not just being switched on. Some systems add further monitoring - such as CO2 or air-quality sensors that can give a pre-alarm and isolate the gas if air quality deteriorates - adding another layer, but the core proving of the ventilation running is what the interlock fundamentally relies on. This is what makes the interlock a genuine safety device: it verifies the extraction is really working before allowing the gas.
What it means for extraction and cleaning
The gas interlock's linking of gas to proven ventilation has an important practical implication: the extraction must genuinely be working for the kitchen to run on gas - which ties the kitchen's operation to keeping the extraction in good working order. Because the interlock cuts the gas if the ventilation is not proven to be running, an extraction that fails, or under-performs to the point where the air-proving does not confirm adequate airflow, can stop the gas and so stop the kitchen. So keeping the extraction working is not just a safety matter but an operational necessity in an interlocked gas kitchen - the kitchen cannot cook on gas without proven ventilation.
This connects to maintenance and cleaning, because a grease-clogged extraction with reduced airflow is one whose performance is degraded - and if the airflow drops far enough, it could affect the air-proving and the interlock. More broadly, the interlock underscores that the extraction genuinely working is essential in a gas kitchen: the gas safety depends on it, and the interlock enforces that dependence. So keeping the extraction clean and performing - so it genuinely moves the air, supplies combustion air and removes the products - is part of the gas safety the interlock protects. The interlock links the gas to the ventilation, but the ventilation has to actually work for that link to keep the kitchen both safe and operating - which depends on the extraction being maintained and cleaned. So the gas interlock, connecting extraction and gas safety, also reinforces why the extraction must be kept working: the gas safety, and the gas supply itself, depend on it. In an interlocked gas kitchen, a working, clean extraction is not optional - it is what lets the kitchen run safely on gas at all.
The takeaway
A gas interlock connects a kitchen's gas supply to its ventilation, so the two cannot be dangerously mismatched. It allows gas to flow to the appliances only while the ventilation is running and proven to be working, and isolates the gas if the ventilation is not - making working extraction a precondition for the gas. This prevents the dangerous situation of gas burning without ventilation, which risks a carbon monoxide build-up, by making the gas physically dependent on the extraction. The 'proven' part is key: the interlock uses an air-proving device - a pressure or airflow switch, or current-sensing on the fan - to verify the extraction is actually running and moving air, not just switched on, so even a fan failure cuts the gas.
So the interlock genuinely ties extraction and gas safety together: gas appliances can only operate when there is proven, working extraction to remove their combustion products and supply combustion air. It is now the minimum standard for new commercial kitchen gas installations, because it directly links the gas safety to the ventilation working. And it has a practical implication - the extraction must genuinely work for the kitchen to run on gas, so keeping it clean and performing is both a safety matter and an operational necessity, since a failed or badly under-performing extraction can stop the gas. In an interlocked gas kitchen, a working, clean extraction is what lets the kitchen run safely on gas - which is exactly the connection the interlock makes and enforces.
Questions
A safety device that connects a kitchen's gas supply to its ventilation, so gas is only allowed to flow to the cooking appliances while the ventilation - extraction and make-up air - is running and proven to be working. If the ventilation is not running or fails, the interlock isolates the gas, so the appliances cannot burn without ventilation. It makes working extraction a precondition for the gas.
Because gas appliances burning without adequate ventilation is dangerous - the extraction supplies the air for clean combustion and removes the products, so gas burning without it can suffer incomplete combustion and let carbon monoxide build up in the kitchen. Linking the gas to the ventilation, so gas cannot flow without the extraction running, prevents that dangerous combination automatically, without relying on people.
It controls the gas supply through a gas valve, opening it (allowing gas) only when the ventilation is running and proven, and closing it (isolating the gas) when the ventilation is not. So the gas cannot flow unless the extraction is running, and if the ventilation stops or fails, the interlock cuts the gas so the appliances cannot burn without ventilation - making the gas physically dependent on the extraction.
That the interlock verifies the extraction is actually running and moving air, not just switched on - because a fan switched on but failed (a broken motor or belt, a blockage) would leave gas flowing without real ventilation. The interlock uses an air-proving device - a pressure or airflow switch in the ductwork, or current-sensing on the fan - to confirm the fan is genuinely working before allowing the gas.
Because checking only that the fan switch is on would give false assurance - the fan could be on but failed, leaving gas burning without ventilation while the interlock thought all was well. By proving the actual airflow or fan operation, the interlock ensures the gas is only allowed when there is real, working extraction, so a fan failure - not just the fan being switched off - cuts the gas. That is what makes the interlock genuinely safe.
The interlock ties the gas to the extraction genuinely working, so the extraction must perform for the kitchen to run on gas - a failed or badly under-performing extraction can stop the gas and so the kitchen. A grease-clogged extraction with reduced airflow is degraded, and if the airflow drops far enough it could affect the air-proving. So keeping the extraction clean and performing is part of the gas safety the interlock protects, and keeps the kitchen operating.
A gas interlock ties the gas to the extraction genuinely working - so keeping the extraction clean and performing is part of the gas safety. Our duct cleaning keeps the extraction moving the air the interlock proves.
