For data centres, UPS and battery rooms, MV switchgear and archives, water is rarely the first choice of extinguishing medium. What the owner wants is a system that extinguishes without residue, does not harm the equipment and is safe in occupied spaces. Three options dominate in practice: HFC-227ea (known as FM-200), FK-5-1-12 (known as Novec 1230) and inert gases.
All three are designed to TS EN 15004 / ISO 14520 and NFPA 2001. The real differences lie less in extinguishing performance and more in storage, enclosure construction and environmental regulation.
How they work
HFC-227ea
Extinguishes through a combination of physical and chemical action, mainly by absorbing heat from the flame. Typical Class A design concentrations are 7 to 9 percent. Discharge must be completed within 10 seconds. The agent is stored as a liquid in cylinders superpressurised with nitrogen.
FK-5-1-12
Works in a similar way at design concentrations usually between 4.5 and 6 percent. It is a liquid at room temperature and vaporises as it leaves the nozzle, which makes transport and handling easier. The margin between design concentration and the accepted human exposure limit is wider than for HFC-227ea.
Inert gases
This group includes IG-541 (nitrogen, argon and CO2), IG-55 (nitrogen and argon) and IG-01 (argon). They extinguish by reducing oxygen in the room to around 12-14 percent, low enough to stop combustion while staying within acceptable limits for short human exposure. Design concentrations are 35 to 50 percent. Agent is stored at 200 or 300 bar and discharge typically takes 60 to 120 seconds.
Comparison
| Criterion | HFC-227ea (FM-200) | FK-5-1-12 (Novec 1230) | Inert gas (IG-541 / IG-55 / IG-01) |
|---|---|---|---|
| Typical design concentration | 7-9 % | 4.5-6 % | 35-50 % |
| Discharge time | 10 s max | 10 s max | 60-120 s |
| Storage footprint | Small | Small | Large (roughly 3-5 times the cylinder volume) |
| Cylinder location | Close to protected room | Close to protected room | Remote cylinder room possible |
| Multi-zone with selector valves | Limited | Limited | Common and economical |
| Pressure relief venting | Required | Required (negative pressure also considered) | Essential, larger vents |
| Global warming potential | High (above roughly 3,000) | Very low (around 1) | Zero |
| Decomposition products | HF possible in fire | HF possible in fire | None |
| Refill and supply | Subject to F-gas restrictions | Supplier transition under way | Easy locally |
Storage space
In an existing building, space is usually the first constraint. A handful of cylinders may be enough with a chemical agent, while the same room might need a full row with an inert gas. On the other hand, inert gas cylinders can sit in a cylinder room tens of metres away and serve several rooms through selector valves. In a building with multiple server rooms, electrical rooms and archives, that can reverse the cost comparison entirely.
Hold time and enclosure integrity
Discharging the agent is only half the job. It has to stay in the room long enough to complete extinguishment and prevent re-ignition. Standards generally require at least 10 minutes, during which the concentration at the height of the highest protected equipment must stay above a defined level.
This is verified with a door fan test. A fan fitted in the doorway pressurises the room, and the hold time is calculated from the measured leakage area. The test should be done at commissioning and repeated after any construction change. Openings above the suspended ceiling, cable penetrations and the void under raised floors are the usual leakage paths.
When agent discharges into a tight room, pressure changes sharply. With inert gases the positive pressure peak is significant. With FK-5-1-12 an initial negative pressure can occur as the vaporising liquid cools the air. Every one of these systems therefore needs a pressure relief vent sized for the strength of the enclosure. In glass-partitioned or lightweight server rooms this deserves serious attention.
Environmental regulation
HFC-227ea is a fluorinated greenhouse gas with a high global warming potential. The EU F-gas Regulation, revised in 2024, follows a phase-down schedule that progressively cuts the quantity of HFCs placed on the market, and Turkish rules on fluorinated gases are moving in a similar direction. Fire protection uses remain within scope with certain exemptions, but shrinking supply affects price and long-term refill availability. If HFC-227ea is chosen for a new project, access to refill agent over a 15 to 20 year system life should be discussed with the supplier.
FK-5-1-12 has a different story. 3M, the best-known producer of the agent under the Novec 1230 brand, ended production at the end of 2025 as part of its exit from PFAS manufacturing. The FK-5-1-12 molecule is now supplied by other manufacturers, and most system manufacturers have been updating their approvals accordingly. For maintenance and refill of existing systems it is worth checking where the agent comes from and whether it matches the system approval. How future PFAS regulation will affect the agent is not yet fully settled.
Inert gases are natural atmospheric components. They face no environmental restrictions and can be refilled locally.
Which one, when
There is no hard rule, but the rough approach we use on site is:
- One small or medium room with little spare space: a chemical agent is the practical choice.
- Several zones to be protected from a single cylinder bank, with space for a cylinder room: inert gas is usually more economical and carries less long-term uncertainty.
- Weak enclosure construction (glass partitions, lightweight walls): solve the pressure relief detail before choosing the agent.
- Operators with environmental targets or long-term certification goals tend to favour inert gas.
Final note
The right choice comes from looking at room dimensions, construction, available cylinder space and the operator’s maintenance plan together. During a site survey ESFA can carry out a preliminary enclosure assessment and work out approximate cylinder quantities and layouts for more than one option, so the decision rests on the actual room rather than a catalogue.