There are fires that water cannot put out. There are installations where a conventional sprinkler would cause as much damage as the fire itself. And there are sectors where response speed is everything, because when an electrical panel or a server room starts to burn, seconds count in a way that no manual extinguisher can cover.
Fixed CO2 extinguishing systems exist precisely for that. They are not an alternative to the portable extinguisher: they are a completely different category, designed to protect critical spaces automatically, without human intervention and without leaving residues that compromise the protected equipment.
This guide explains how they work, where they are installed, what they are made up of and what regulations you must comply with if you are considering implementing one in your industrial installation.
What is a CO2 extinguishing system and why is it not the same as an extinguisher
A fixed CO2 extinguishing system is a permanent installation that stores carbon dioxide in liquid state at high pressure and discharges it in a controlled manner over the risk area when a fire is detected. Everything happens automatically, in seconds, and without anyone having to activate anything.
The difference with a portable CO2 extinguisher is not only size. It is conceptual. The portable extinguisher depends on someone being present, detecting it in time and applying it correctly. The fixed system eliminates all those variables.
How CO2 acts on fire
CO2 extinguishes fire through two combined mechanisms: suffocation and cooling.
When discharged, it displaces oxygen from the air in the protected area. Fire needs a minimum oxygen concentration to remain active —usually above 15%—. When CO2 reduces that concentration below the threshold, the fire goes out.
At the same time, CO2 expands rapidly when passing from liquid to gas state, which generates a sudden drop in temperature that contributes to cooling the source.
The result is fast, clean extinguishing that does not damage protected equipment. There is no water, no powder, no foam. Only gas that dissipates and leaves the equipment in condition to operate again after an inspection.
Total flooding vs. local flooding: which applies in each case
Here there is a distinction that many installations are not clear about and that conditions the entire design of the system.
Total flooding means that CO2 completely fills the volume of the protected enclosure until it reaches the design concentration necessary to extinguish the fire. For it to work, the enclosure must be relatively airtight —doors, windows and ventilation ducts must be able to close automatically at the time of discharge—. It is the most common mode in server rooms, electrical panels or archives.
Local flooding concentrates the discharge directly over the equipment or risk area, without the need to flood the entire enclosure. It is used when the risk is well defined —for example, a printing machine, a transformer or a painting area— and the surrounding space cannot be effectively isolated.
Choosing the wrong mode is not only a matter of effectiveness: it also affects the calculation of the amount of agent, the design of the distribution network and regulatory compliance.
Where these systems are installed (and where they should not be installed without further consideration)
Sectors and spaces with the highest demand
CO2 extinguishing systems are especially suitable when two conditions coincide: the fire risk is real and water or other agents would cause unacceptable damage to the protected equipment or materials.
The most common environments include:
- Server rooms and data centres: where service continuity is critical and humidity is incompatible with operation.
- High-voltage electrical panels: where water is directly dangerous.
- Generators and transformers: high-value equipment with fire risk in dielectric oil.
- Printing plants and machine rooms: with the presence of oils, solvents or large quantities of paper.
- Warehouses of flammable materials: combustible liquids and solids where rapid extinguishing is essential.
- Naval and offshore sector: holds, engine rooms of vessels and platforms.
- Food and pharmaceutical industry: where residues from other extinguishing agents would compromise production.
Limitations: environments not suitable for CO2 without additional measures
CO2 in concentrations above 7-9% is dangerous for people. Above that level, it causes loss of consciousness and, at typical design concentrations —between 34 and 75% depending on the type of fire—, it can be lethal in brief exposure.
This does not mean that CO2 cannot be used in spaces where there is personnel: it means that in these cases the system requires discharge delays, acoustic and light signalling, and verified evacuation procedures. The regulations are very clear in this regard.
The spaces where CO2 is directly not viable are those with permanent personnel who cannot evacuate quickly —for example, continuous production areas with operators who do not have a clear exit within seconds—. In these cases, alternative agents such as inert gases or water mist systems must be assessed.
Components of a fixed CO2 system: what lies behind the installation
A CO2 extinguishing system is not simply a large bottle with a pipe. It is an integrated installation with several subsystems that must operate in a coordinated way.
Tanks, cylinder banks and manifolds
CO2 is stored in high-pressure cylinders —at around 50-60 bar at room temperature— or in low-pressure tanks refrigerated at around -18 °C. The choice depends on the amount of agent required.
For small or medium-sized installations, the most common solution is cylinder banks connected in parallel to a common manifold. For large installations —or when storage space is limited and a large amount of agent is required—, low-pressure tanks are more efficient.
The amount of CO2 required is calculated based on the volume of the enclosure, the type of risk, enclosure leaks and the retention time required according to regulations.
Pipe network and discharge nozzles
The system distributes CO2 from the tanks to the discharge nozzles through a pipe network sized to guarantee the appropriate pressure and flow rate at each point. Hydraulic design is one of the most critical aspects of the installation: a calculation error can mean that the design concentration is not reached throughout the protected area.
The nozzles are designed and positioned to ensure homogeneous distribution of the agent. In total flooding, position matters as much as number: poor distribution creates areas with insufficient concentration where the fire can continue.
Detection and discharge control panel
The system does not operate alone. It is connected to a fire detection control panel that processes the signals from the detectors installed in the protected area —smoke, temperature, flame or combined detectors—. When the control panel confirms the alarm, it activates the discharge sequence.
That sequence usually includes: activation of acoustic and optical alarms, automatic closure of ventilation and enclosure doors, configurable delay to allow evacuation, and finally opening of the discharge valves.
The system must also include a manual discharge mode so that authorised personnel can activate or cancel it if necessary.
How the system is activated: automatic and manual discharge modes
A well-designed system can be activated in three ways:
Automatic discharge: the detection control panel receives a signal from one or more detectors, confirms the alarm —normally by double confirmation to avoid false alarms— and activates the discharge after the programmed delay. This is the usual mode in normal operation.
Local manual discharge: from a push button located outside the protected enclosure, personnel can activate the discharge manually without going through the control panel. Useful when the operator visually detects the fire before the sensors.
Remote manual discharge: from the control panel or from a remote panel, the operator can activate or inhibit the system. Especially relevant in installations with multiple protected zones managed from a single point.
The system must also have an inhibition mode —for maintenance work inside the enclosure— and safety interlocks that prevent accidental discharge when there is personnel inside without the possibility of evacuation.
Regulations governing CO2 extinguishing systems in Spain
Fire Protection Installations Regulation (RIPCI)
The RIPCI —Royal Decree 513/2017— is the main regulatory framework for all fire protection systems in Spain, including gaseous agent extinguishing systems. It establishes the conditions for design, installation, maintenance and inspection, as well as the requirements for installation and maintenance companies.
Any installation of a fixed CO2 system must be carried out by a company authorised as an installer of fire protection systems, and must be documented with the corresponding installation certificate.
UNE-EN 15004 standard: technical design requirements
The UNE-EN 15004 standard is the specific technical reference for gaseous agent extinguishing systems, including CO2. It establishes the system design requirements: calculation of the amount of agent, minimum design concentration according to the type of risk, retention time, enclosure tightness tests and safety conditions for people.
Compliance with this standard is not optional when it comes to obtaining the technical documentation required for legalising the installation.
Maintenance and periodic inspection obligations
The RIPCI establishes a mandatory maintenance programme with three levels:
- Quarterly maintenance: visual check of the general condition of the system, review of signage, verification of the condition of the cylinders and check of the detection control panel.
- Six-monthly maintenance: detector testing, checking of discharge circuits, verification of the condition of valves and nozzles.
- Annual maintenance: complete system inspection, weighing or checking of the CO2 level in the tanks, full installation test and documentation update.
Each maintenance operation must be recorded in the building logbook and certified by the authorised maintenance company.
What to consider before installing a CO2 system in your plant
Installing a CO2 extinguishing system is not a decision that should be made only by looking at the catalogue. There are variables that determine whether CO2 is the right solution, what type of system is most suitable and what real budget it involves.
Before moving forward, it is advisable to have answers to these questions:
Is the enclosure sufficiently airtight? A leak analysis of the enclosure is essential before design. If the enclosure loses CO2 faster than the system can maintain the concentration, the system does not work. Sometimes the cost of sealing the enclosure exceeds the cost of the system itself.
Is there personnel working inside or near the protected enclosure? This does not rule out CO2, but it requires designing a verified evacuation protocol, with discharge delays, adequate signalling and staff training. Regulations require it and safety demands it.
What is the real risk that needs to be protected? Not all risks have the same design concentration or the same retention time. A fire in transformer oil is not designed in the same way as one in paper or electronic equipment. The design must be specific to the risk, not generic.
Is the installation integrated with the rest of the fire protection systems? The CO2 system must be coordinated with the building’s general detection system, with ventilation systems, with fire doors and with the emergency plan. An isolated installation that does not communicate with the rest of the protection system creates dangerous blind spots.
Are you assessing the installation of a CO2 extinguishing system in your plant or industrial installation? At Fleximecan we have spent years designing and installing fire protection systems for industry. Contact our technical team and we will help you find the right solution for your specific risk.