The chemical industry does not burn like a cardboard warehouse. It burns with class B fires that spread across the floor, with explosive atmospheres that turn a spark into a detonation, with reagents that react with the water from the extinguisher and worsen the fire. And it does so in installations where stopping production has a cost that sometimes rivals that of the incident.
That changes everything in terms of extinguishing system design.
This article does not explain what an automatic sprinkler is. It explains which system is chosen in each type of chemical installation, why the other options were discarded and which technical conditions — type of agent, geometry of the installation, regulations— determined the decision. The scenarios are representative of real situations in the sector.
Why the chemical industry needs a different approach to fire protection
Most fire protection regulations are designed for buildings: offices, logistics warehouses, shopping centres. The chemical industry has risks that these regulations do not adequately cover on their own.
The first problem is the type of fire. Flammable liquids generate class B fires that cannot be extinguished with conventional water —water can spread the fuel instead of smothering it—. Pressurised gases produce class C fires that require cutting off the supply before extinguishing, not afterwards. And some reagents —alkali metals, certain peroxides— react violently with water and turn a controllable fire into a larger-scale incident.
The second problem is the environment. Many areas of a chemical plant are classified as ATEX zones, which not only affects electrical equipment: it also determines the design of the detection system, valve actuators, the detectors themselves and any component that could generate an ignition source.
Class B, C and special fires: the challenges that a standard system does not solve
A standard water sprinkler system covers class A fires —organic solids— well under normal conditions. In chemistry, that scenario is the exception.
Class B fires —flammable liquids— require agents that form a barrier between the fuel and oxygen: foams, powders or gases. Class C fires —flammable gases— should not be extinguished until the source has been cut off: extinguishing the flame without cutting off the gas creates a much more dangerous explosive accumulation. And special fires involving reactive metals or materials that react with water require specific agents —special D powders, dry sands— that are not part of any conventional system.
The choice of extinguishing agent is not a design detail. It is the first strategic decision of the system.
ATEX zones and their impact on the design of any extinguishing system
The ATEX classification divides installations into zones according to the probability of explosive atmospheres being present: Zone 0, 1 and 2 for gases and vapours; Zone 20, 21 and 22 for dusts. The greater the risk, the more restrictive the requirements for the equipment that can be installed there.
A fire detector in Zone 1 must have ATEX category 2G certification as a minimum. A pneumatic discharge valve may be suitable where an electric one would be ruled out. Cables must run through conduits suitable for the zone. And the extinguishing system itself —if it generates aerosols or particles— must be assessed to ensure that it does not itself create a risk in the environment.
Designing an extinguishing system without integrating the ATEX classification from the outset is not a simplification: it is a project error that can legally invalidate the installation.
Case 1 — Chemical product storage rooms with class A and B fire risk
The typical scenario and its conditions
A chemical manufacturing plant has indoor warehouses where solid raw materials —class A— coexist with containers of flammable liquids in limited quantities —class B—. The space is enclosed, with metal shelving up to four metres high, controlled ventilation and access restricted to authorised personnel.
The risk is not a large spill: it is a heat source in a cardboard box, a damaged container releasing vapours, or a short circuit in an auxiliary warehouse panel. A fire that is not under control within five minutes becomes a total loss.
The main condition is that there is packaged material —cardboard, plastic, labels— that accelerates propagation. And that many of the stored products do not tolerate water: water in a drum of organic solvent can disperse the product and spread the fire instead of extinguishing it.
Why CO2 is the right solution in enclosed storage spaces
In an indoor warehouse with good tightness, the CO2 system by total flooding solves the underlying problem: it acts on the fire without leaving residues, without damaging stored products that have not burned, and without introducing water into an environment where water is counterproductive.
The system discharges CO2 into the volume of the enclosure until it reaches the design concentration —usually between 34 and 50 %— that eliminates the oxygen needed to sustain combustion. The discharge is fast, homogeneous and reaches all points of the warehouse, including areas that a manual extinguisher would not reach in time.
The system components —CO2 cylinders, discharge valves, manifolds and diffusers— are sized according to the volume of the enclosure and the type of risk, following the UNE-EN 15004 standard. Detection is integrated with smoke or temperature detectors, and discharge includes a delay and acoustic signalling to ensure evacuation before discharge.
What must be verified before installation: the tightness of the enclosure
CO2 works if the enclosure retains the gas long enough to extinguish the fire and prevent it from reigniting. If the warehouse has significant leaks —gaps in suspended ceilings, ventilation ducts without automatic closure, doors with poor seals—, the design concentration is not maintained and the system loses effectiveness.
That is why the design process always includes an analysis of enclosure leaks. In many projects, the cost of correcting these leaks —sealing ducts, installing automatic closures on doors and ventilation— forms part of the installation budget. It is not an extra: it is a requirement for the system to work.
Case 2 — Control rooms and electrical panels in chemical plants: when CO2 is not safe enough for personnel
The typical scenario and its conditions
A chemical plant has a central control room where the SCADA systems and PLCs that manage the process operate. The room is air-conditioned, has restricted access and houses high-value electronic equipment whose loss would halt production for days or weeks.
The fire risk in this type of room is well known: electric arc, cable overheating, power supply failure. What changes compared with a conventional server room is that in chemistry there may be operators working in the room during process emergency situations —just when the fire risk is highest.
FM-200 (HFC 227ea): the advantage of a clean agent with a greater safety margin for people
CO2 extinguishes well, but at design concentrations —between 34 and 50 % of the volume— it is dangerous for people. If there is an operator in the room at the time of discharge who cannot evacuate within the delay seconds, the risk is serious.
The FM-200 gas (HFC 227ea) solves this problem. It works by absorbing and extracting heat from the flames until the temperature drops below the combustion point, extinguishing the fire without significantly displacing oxygen. Its NOAEL —no observable adverse effect level— allows its use in occupied areas with total flooding systems, something that CO2 cannot guarantee at equivalent design concentrations.
The practical result: the system can be activated even if there is personnel in the room, with the appropriate delay times and signalling, without the discharge itself representing a risk for anyone who has not been able to evacuate. In a chemical control room with permanent operators, that difference is not minor.
Clean agent, zero secondary damage to equipment
In addition to safety for people, FM-200 has another critical advantage in control rooms: it leaves no residues. After discharge, the electronic equipment is not contaminated or damp. Once the room has been ventilated and the installation inspected, the equipment can return to operation without cleaning or replacing components.
This contrasts with what happens with water or powder: a fire extinguished with these agents in a control room is equivalent, in practice, to a complete renewal of the electronics. The cost of the clean agent is more than recovered in the first incident.
Case 3 — Laboratories and technical rooms in chemical plants: when the space is small and the risk is high
The typical scenario and its conditions
Quality control laboratories and technical rooms in a chemical plant share a characteristic that makes them especially vulnerable: they are small spaces, with high-value equipment —chromatographs, analysers, spectrometers— and with regular personnel presence.
The fire risk comes from varied sources: a poorly extinguished Bunsen burner, a reagent spilled onto a hot plate, electrical equipment overheating. Most laboratory fires start small. The problem is that in a confined space, with combustible material nearby, they can grow very quickly.
A total flooding system with CO2 in a laboratory with regular personnel has the same safety problems as in the control room: the design concentration is incompatible with the presence of people without very robust additional measures.
FM-200 or FE-13 depending on the temperature of the environment
For laboratories and technical rooms, HFC gases are the natural solution. FM-200 (HFC 227ea) is the most common option: clean agent, residue-free, safe for people at the design concentrations needed to extinguish class A and B fires, and compatible with the sensitive equipment that must be protected.
In laboratories where operating temperatures are low —preservation chambers, chromatography rooms with refrigerated equipment— FE-13 (HFC 23) has a specific technical advantage: its significantly lower boiling point than FM-200 allows the agent to discharge correctly even in cold conditions where other gases would have flow problems. At the same design concentration, FE-13 maintains its effectiveness where FM-200 might not discharge with adequate pressure.
The choice between one and the other is not a matter of preference: it is determined by the temperature of the enclosure, the type of risk and the hydraulic calculation of the system.
What these cases have in common: design criteria that must not be skipped
Four different scenarios, four different solutions. But there are a series of criteria that appear in all of them and that mark the difference between a system that works at the critical moment and one that only fulfils the paperwork.
The extinguishing agent is chosen according to the fuel and the environment, not according to the budget. CO2 is more economical than FM-200. FM-200 is safer for people. FE-13 works where FM-200 fails in the cold. Choosing the wrong agent because of cost does not save money: it guarantees that the system will not extinguish or that the extinguishing will create a safety problem.
The tightness of the enclosure is not a given: it is measured. All total flooding systems —CO2 or HFC gases— depend on the enclosure retaining the agent for long enough. Without a leak analysis prior to design, the system may be perfectly installed and still be ineffective.
Detection determines effectiveness. An automatic system is only as fast as its detection. In laboratories, point detection integrated into the equipment can be more effective than conventional perimeter detection. The type of detector is not a secondary detail: it defines the real response time.
Safety for people is not negotiable. In spaces with regular personnel, the choice between CO2 and a clean agent such as FM-200 has direct consequences for operator safety. That choice must be documented and justified in the project.
Maintenance is part of the design. A system with components that are difficult to access, without available spare parts or that requires total emptying of the agent for any inspection, ends up being a system that is not maintained. And a system that is not maintained is not protection: it is documentation.
Do you have a chemical installation with specific risks and need to assess which extinguishing system is the right one? At Fleximecan we analyse each project based on the real risk, not from the catalogue. Contact our technical team.