Where water is unacceptable, gas takes over: server rooms, archives, generators, cable galleries, museum stores. But gaseous suppression is not one technology; there are four families and four different risk profiles.
Four families
| Criterion | FM200 (HFC-227ea) | NOVEC 1230 (FK-5-1-12) | IG-541 (Inergen) | CO2 |
|---|---|---|---|---|
| Suppression mechanism | Chemical plus heat absorption | Heat absorption | Oxygen dilution | Oxygen dilution |
| Minimum design concentration, Class A / Class C (NFPA 2001 Table A.7.2.2.3(b); higher for Class B fuels) | 6.7 / 7.0 percent | 4.5 / 4.5 percent | 34.2 / 38.5 percent | 34 percent and above (NFPA 12) |
| Occupied spaces | Suitable (below the 9 percent NOAEL) | Suitable, widest margin (NOAEL 10 percent) | Suitable (NOAEL 43 percent, i.e. at least 12 percent oxygen) | Not suitable — lethal |
| Storage | Liquefied, few cylinders | Liquid, low pressure | Compressed gas, many cylinders | Liquefied |
| Cylinder room area | Small | Small to moderate | Large (3 to 5 times) | Moderate |
| Global warming potential | High (GWP 3,350; NFPA 2001 Table A.4.6, IPCC 2013) | Very low (GWP below 1) | Zero (atmospheric gases) | Low |
| Regulatory risk | Under F-gas restriction | Low | None | None |
| Discharge time (NFPA 2001 7.5.1) | 10 seconds maximum | 10 seconds maximum | 60 s maximum (Class B) / 120 s (Class A and C) | Variable |
| Pressure relief | Required | Required | Large damper required | Required |
| Residue | None | None | None | None |
| Cost | Moderate | High | Moderate (cylinder room is costly) | Lowest |
Three questions that decide the choice
- Are there people in the space? If so, CO2 is out. CO2 is lethal at its design concentration (34 percent and above) and is used only in unoccupied spaces, with locked access and a delay siren.
- How much room is there for cylinders? IG-541 is a compressed gas and needs 3 to 5 times the cylinders of FM200 for the same volume. Without the space, the list narrows itself.
- What is the regulatory horizon? FM200 is under F-gas restriction. For a data centre to be operated for twenty years, NOVEC or IG-541 is the safer bet.
Do not forget pressure relief. Gas discharge creates a sudden pressure rise in the room; without a relief damper, plasterboard walls and suspended ceilings blow out. IG-541's discharge is longer (60 to 120 seconds) but needs the largest damper section. This is the item noticed last and paid for most dearly on most projects.
Integrity: the system's real performance
A gaseous system works only if the enclosure holds. A door fan test measures the retention time of the enclosure; NFPA 2001 7.4.1 requires at least 85 percent of the minimum design concentration to be held at the highest level of protected content for 10 minutes. Cable penetrations, the gap under the door, connections above the suspended ceiling and ventilation dampers are the leakage paths. The system should not be accepted at commissioning without passing the door fan test — it is the most frequently skipped test on site.
Use alongside sprinklers
The common arrangement in a data centre is gaseous suppression plus pre-action sprinklers. The gas is the first line of defence; if it fails or the fire grows, the sprinklers take over. In that arrangement the sprinklers are chosen as double interlock, so the accidental discharge risk approaches zero. The release logic of the two systems must be coordinated at the fire alarm panel; sprinklers must not open while the gas is discharging.
Turkish context
BYKHY Article 98(3) bases the design of gaseous extinguishing systems on TS ISO 14520 and requires audible and visual warnings that tell occupants the agent is discharging; Article 98(4) requires vents and ventilation ducts of the protected room to close automatically on detection and discharge. BYKHY does not reference EN 15004 or NFPA 2001. In practice NOVEC 1230 is common in data centre and archive projects, IG-541 or FM200 in generator rooms and cable galleries, and CO2 in unoccupied industrial spaces. Where the insurer requires it, an FM Approved system condition arrives and the option list narrows further.
Frequently Asked Questions
Can CO2 be used in an occupied space?
No. CO2 is lethal at its design concentration and is used only in unoccupied spaces, with locked access and a delay siren. NOVEC, FM200 or IG-541 are preferred where people are present.
Why is a door fan test mandatory?
A gaseous system works only if the enclosure holds. The door fan test measures the retention time; NFPA 2001 7.4.1 requires at least 85 percent of the minimum design concentration to be held at the highest level of protected content for 10 minutes (or long enough for trained personnel to respond). The system should not be accepted until it passes.
Why does IG-541 need more space?
IG-541 is a compressed gas rather than liquefied. It needs 3 to 5 times the cylinders of FM200 for the same protected volume, so the cylinder room area directly affects the choice.
Does gaseous suppression replace sprinklers?
Usually not. The common data centre arrangement is gas plus double interlock pre-action sprinklers: the gas is the first defence and the sprinklers the second layer.
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Download MEP Calc on the App StoreThe EN 15004 series (gaseous extinguishing systems) and ISO 14520. NFPA 2001 Standard on Clean Agent Fire Extinguishing Systems. NFPA 12 (CO2). Turkish Regulation on Fire Protection of Buildings (BYKHY) Article 98. Design concentrations and NOAEL values are taken from the manufacturer's certificate and the full text of the standard.