A professional kitchen in full service is one of the environments with the highest fire risk in any sector. Fryers at 180 °C, red-hot griddles, hoods with grease build-up, and a work pace that leaves no room to react when something goes wrong.
The problem with grease fires is not only that they are frequent. It is that they are fast, silent at first, and that they react badly to first instincts: pouring water onto a fryer in flames does not extinguish the fire, it turns it into an explosion of steam and incandescent grease.
That is why the automatic extinguishing system for industrial kitchens exists. Not to replace people, but to act at second zero, before the fire has time to grow.
This guide explains how this system works, what components it consists of, what options exist and what the regulations require.
The real risk of an industrial kitchen: why a manual extinguisher is not enough
A manual extinguisher has two critical limitations in a professional kitchen. The first is that it depends on someone seeing it, picking it up, using it correctly and arriving in time. The second is that in a service with several cooks, smoke, noise and pressure, the detection of an incipient source can arrive several minutes late.
Several minutes is a long time when hot grease is involved.
Class F fires: what makes grease different as a fuel
Grease fires —cooking oils and fats— are classified as class F, a specific category that did not exist in the original European classification precisely because their behaviour is different from that of any other liquid fuel.
Cooking grease has a flash point that can exceed 300 °C, but when it reaches that temperature —which happens in a fryer without a thermostat or with a faulty thermostat— the oil does not just burn: it burns with an intensity and a propagation speed that surprises even those who have already seen it.
In addition, the grease accumulated in the extractor hood, in the filters and inside the ventilation ducts creates a fuel reservoir that can turn a small fire into an incident affecting the entire installation.
Why a fire in a fryer cannot be extinguished with water
It is the most dangerous mistake someone without training can make when faced with a grease fire: pouring water on it.
The water comes into contact with the oil at more than 300 °C and vaporises instantly, expanding its volume between 1,500 and 1,700 times in fractions of a second. That steam carries droplets of incandescent oil with it in all directions. The result is a fireball that can cause serious burns to anyone nearby and spread the fire throughout the kitchen in seconds.
An automatic system with the correct extinguishing agent does not make that mistake. It acts specifically on the grease, without water, without human intervention and without depending on someone being present.
What components make up an automatic extinguishing system in a kitchen
An automatic extinguishing system for kitchens is not simply a bottle connected to some nozzles. It is an integrated installation with several elements that must operate in coordination within a matter of seconds.
Detection system: heat-sensitive tube vs. electronic detection
Detection is the first link. Without fast and reliable detection, the rest of the system cannot act in time.
The most common method in kitchens is the heat-sensitive tube: a flexible polymer tube that is installed directly in the hood or above the cooking equipment. When the temperature at any point of the tube exceeds the design threshold —usually between 140 and 182 °C depending on the system—, the tube deforms or breaks at that point and mechanically activates the discharge of the agent. It does not need electricity, it does not need a signal from any control panel: it is a purely physical mechanism that works even if there is a power supply cut.
Electronic detection —through temperature sensors or flame detectors— allows more sophisticated integration with the premises’ alarm control panel and offers continuous supervision of the system’s status, but it requires electrical power and additional control logic.
Extinguishing agent and tank
The extinguishing agent is the element that puts out the fire. In industrial kitchens, the most commonly used agents are specific for class F fires: aqueous solutions with additives that react with hot grease, forming a soap layer that seals and smothers it, or high-pressure water mist that combines smothering, cooling and mist effect.
The agent is stored in a pressurised tank or cylinder that remains ready to discharge at any time. The size of the tank depends on the number of protected appliances and the surface area of the hood.
Distribution network and discharge nozzles
From the tank, the agent reaches the discharge points through a pipe network —usually stainless steel in kitchen environments— that ends in nozzles strategically positioned over each cooking appliance: fryers, griddles, woks, salamanders.
The position of the nozzles is not arbitrary. Each one is calculated to cover the surface of the appliance with the correct angle and flow rate. A poorly positioned nozzle may not reach the source or may discharge the agent in a direction that does not smother the flame.
Automatic gas or electricity supply cut-off
This component is as important as the extinguishing agent, and yet it is the one that is most underestimated.
When a fire is detected, the system not only discharges the agent: it also automatically cuts off the energy supply to the cooking equipment. If the heat source remains active —the burner on, the electrical resistance energised—, the agent may momentarily extinguish the fire but the grease reignites in seconds because the surface remains at ignition temperature.
The gas cut-off is carried out by means of a solenoid valve in the supply line that closes when the system is activated. The electrical cut-off is managed by means of a contactor. Both must be manually reset after the incident, which prevents the kitchen from operating again without someone having checked the condition of the system.
How the system acts when a fire occurs: the complete sequence
Under normal conditions, the system is in permanent standby mode. It does not consume significant energy, does not interfere with the work of the kitchen and does not require any action by the staff.
Detection of the source
The first event is detection. In systems with heat-sensitive tube, detection is instantaneous at the point where the temperature exceeds the threshold: the tube reacts in milliseconds. In systems with electronic detection, the response time depends on the type of sensor and the confirmation logic configured in the control panel.
At that moment —and only at that moment— the system exits standby mode and activates the extinguishing sequence.
Energy cut-off and activation of discharge
The action sequence has a precise order: first the energy cut-off, then the discharge of the agent.
The energy cut-off eliminates the heat source. The discharge of the agent acts on the active source. If it were done the other way round —discharging first and cutting off afterwards—, the agent could momentarily extinguish the fire but the heat source would remain active and cause almost immediate reignition.
All this happens in less than one second from detection.
Action of the agent on burning grease
The extinguishing agent reaches the surface of the burning grease and acts through several simultaneous mechanisms. It cools the grease below its ignition temperature. It forms a surface layer that isolates it from oxygen. And in the case of water mist, it generates steam that displaces oxygen in the immediate area of the source.
The result is the extinguishing of the fire in the first seconds of discharge, without the agent causing additional damage to the equipment or to the food that was being prepared.
After discharge, the kitchen must remain closed long enough for the agent to act completely. Ventilation is only restored when it is confirmed that there is no risk of reignition.
Fleximecan’s own system
There is no single valid system for all kitchens. The size of the installation, the type of cooking equipment, the configuration of the hood and the level of integration with the premises’ general alarm determine which solution is the most suitable.
Fleximecan system: configurable valve with dual activation
Fleximecan has developed its own detection and extinguishing system for industrial kitchens, designed from installation practice to solve the specific problems presented by real professional kitchens.
The central element is an innovative valve configurable for both direct and indirect extinguishing, which allows the same system to be adapted to different hood and equipment configurations without changing the main components.
The system has two activation modes: by means of a heat-sensitive tube —automatic activation without the need for electricity— and by means of manual activation next to the tube pressure indicator manometer, which allows kitchen staff to activate the system directly if they detect a fire before the tube itself.
Added to this is the automatic cut-off of the gas supply to all protected cooking equipment at the time of discharge, eliminating the heat source simultaneously with extinguishing. The extinguishing agent used offers effective extinguishing for class A, B and F fires, covering all the typical risks of a professional kitchen.
What the regulations say: when it is mandatory and what inspections they require
Installations required under the RIPCI
The Fire Protection Installations Regulation —Royal Decree 513/2017, RIPCI— establishes which installations are required to have automatic extinguishing systems in kitchens.
The obligation applies to industrial kitchens with installed power in the cooking appliances above 50 kW. For practical purposes, this includes the vast majority of professional kitchens in restaurants, hotels, hospitals, care homes, collective dining rooms and any establishment with meal production at scale.
The installation must be carried out by a company authorised as an installer of fire protection systems, and must be documented with the corresponding installation certificate that forms part of the premises’ documentation for any inspection by the fire brigade or the competent authority.
Maintenance programme and periodic inspections
The RIPCI establishes a mandatory maintenance programme with two levels for this type of system:
Quarterly maintenance includes the visual check of the general condition of the system, verification that the nozzles are not blocked by accumulated grease, checking the condition of the heat-sensitive tube and reviewing the signage. In kitchens, grease build-up on the nozzles is one of the most frequent and silent failures: the system appears to be in perfect condition but blocked nozzles would not discharge correctly in the event of a fire.
Annual maintenance includes the complete inspection of the system, verification of the agent pressure in the tank, checking the operation of the discharge mechanisms and the automatic energy cut-off, and updating the documentation. It must be carried out by an authorised maintenance company and recorded in the building logbook.
Signs that your current system is not working properly
Having a system installed is not enough if that system is not in a condition to act when you need it. These are the most common signs that something is not right:
Nozzles with visible grease build-up. In an active kitchen, grease impregnates everything. If the discharge nozzles show hardened grease, the agent will not come out with the correct pressure and angle. It is the most frequent problem and the easiest to detect visually.
The heat-sensitive tube has marks, bends or deformations. The tube must be taut, well secured and without visible deterioration. A tube with kinks or crushing may not respond correctly to temperature or may break at a point that is not over the risk source.
There is no maintenance record for the last 12 months. If there is no annual maintenance certificate signed by an authorised company, the system has not been properly inspected. This is not only a regulatory breach: it is not knowing whether the system would work in the event of a fire.
The system is not connected to the gas cut-off. There are old installations where the extinguishing system discharges the agent but does not have the automatic energy cut-off integrated. In those cases, extinguishing is partial: the agent may momentarily put out the fire but the heat source remains active.
No one in the kitchen knows how to activate it manually. The automatic system acts on its own, but in situations where automatic detection has not worked or there is a source that staff see before the tube, manual activation is the second line of defence. If no one knows where the manual push button is or how to use it, that line of defence does not exist.
Do you have an industrial kitchen and want to know which extinguishing system best suits your installation? At Fleximecan we install and maintain extinguishing systems for professional kitchens. Contact our technical team.