Technical·14 min read
Clean-Agent Gas Suppression: Working Principle, Design and Agent Selection
Gas suppression demands correct design as much as the right agent. We examine the extinguishing physics, the storage and room-pressure factor, agent comparison and central-system advantages from an engineering perspective; as A-Pro, we explain our recommendation of NOVEC 1230 among chemical clean agents and argon among inert gases.
A-Pro Engineering
Gas fire suppression is the method of choice in electrical/electronic spaces where water would cause damage — but delivering the right result depends on correct design as much as on selecting the right agent. You can find which building/space types require gas suppression in our general guide (Turkish Fire Code (BYKHY) Article 98); in this article we go into the engineering side: how the system physically extinguishes the fire, why pressure is a critical factor, which agent we recommend and why, and what advantages a central system brings.
Extinguishing physics: two distinct mechanisms
“Gas suppression” is not a single method; it is built on two separate physical principles:
- Chemical clean agents (FM200, NOVEC 1230): Extinguish mainly by absorbing heat — they draw from the environment the heat needed to sustain the flame, and partly break the combustion chain reaction. They typically reach the design concentration in ≈10 seconds.
- Inert gases (argon, nitrogen): Extinguish by reducing the oxygen in the space to the level at which combustion stops. Pure argon (IG01) brings the room oxygen down to about 12.5%; this is a range low enough for the flame to extinguish yet safe for controlled evacuation.
Both families share three common characteristics: they leave no residue, are electrically non-conductive, and equipment continues to operate after suppression. The difference is how they achieve extinguishing and — as we will see shortly — how they are stored.
Agent families: comparison
| Criterion | FM200 (HFC-227ea) | NOVEC 1230 (FK-5-1-12) | Argon (IG01) | Inergen (IG-541) | CO₂ |
|---|---|---|---|---|---|
| Extinguishing | Heat absorption + chain breaking | Predominantly heat absorption | O₂ dilution (≈12.5%) | O₂ dilution + partial CO₂ | O₂ smothering + cooling |
| Storage pressure | 25 / 42 / 50 bar (liquid) | 25 / 42 / 50 bar (liquid) | 200–300 bar | 200–300 bar | ≈50–60 bar (liquid) |
| Footprint | Least | Low | High (many cylinders) | High (many cylinders) | Medium |
| Discharge time | ≈10 s | ≈10 s | 60–120 s | 60–120 s | Variable |
| Occupied space | Suitable | Very suitable (wide NOAEL) | Suitable | Suitable | Not suitable (unoccupied) |
| Environmental impact | High GWP | GWP ≈1, lifetime ≈5 days | Zero GWP/ODP | Zero GWP/ODP | Asphyxiant, GWP ≈1 |
| Refill | High (imported gas) | High (imported gas) | Low (locally available) | Low (locally available) | Low (locally available) |
How does the table guide the customer’s choice? If an occupied space is involved (server room, control room), CO₂ is eliminated; if environmental priority and sustainability are paramount, NOVEC 1230 or inert gases come to the fore; if the cylinder-room area is limited, chemical gases stored compactly (FM200, NOVEC) are advantageous; if operating/refill cost is the deciding factor, inert gases take the lead.
FM200, NOVEC 1230 and inert gases (argon, Inergen) are engineered according to the TS ISO 14520, EN 15004 and NFPA 2001 standards; CO₂ systems, on the other hand, are subject to a separate standard (TS ISO 6183 / NFPA 12). While CO₂ is a powerful extinguishing agent, because it lowers oxygen by smothering it is not used in occupied spaces; it is suitable only for unoccupied technical volumes (generators, turbines, flammable-liquid stores).
Refill cost is an item often overlooked in selection but decisive from an operating standpoint. FM200 and NOVEC 1230 are imported chemical gases; although refilling can be done in Turkey, their refill cost is high. Inert gases (argon, nitrogen and the Inergen components), on the other hand, are gases already present and available everywhere in our country, so their refill cost is low — restoring the system to service after a discharge is far more economical.
The pressure factor: from storage to room safety
Pressure is one of the most overlooked yet most critical parameters of gas suppression design. It is decisive at two separate levels:
1. Storage pressure. Chemical clean agents (FM200, NOVEC 1230) are liquefied and held with nitrogen at relatively low pressure (typically 25, 42 or 50 bar); this allows them to be stored compactly in a small number of cylinders. Inert gases, on the other hand, are stored as compressed gas at high pressure such as 200–300 bar — which means more and heavier cylinders and therefore a larger cylinder room. However, this high pressure is as much a design advantage as a drawback: it can carry the gas over much longer distances (see the “pipe length” heading below).
2. Room pressure on discharge. When the gas discharges into the space, the pressure inside the room rises abruptly. If this pressure is not balanced, walls, suspended ceilings and doors may be damaged; worse, the room integrity may be compromised, the gas escapes and extinguishing fails. Therefore the space must have a correctly sized pressure relief damper that safely relieves the pressure at the moment of discharge. Because they produce large volumes of gas, this damper is mandatory especially for inert gases.
In short, pressure directly affects both the cylinder-room sizing and the structural safety of the protected space.
The A-Pro approach: NOVEC 1230 and argon
Although many agents are available on the market, as A-Pro Engineering we offer a clear recommendation in two families:
- Among chemical clean agents, NOVEC 1230 (FK-5-1-12). With a global warming potential of ≈1 and an atmospheric lifetime of ≈5 days, it is the best of the clean agents from an environmental standpoint; the wide margin between the design concentration and the safety threshold (NOAEL) provides additional confidence in occupied spaces. It is the most balanced choice for facilities where sustainability and insurance are priorities.
- Among inert gases, pure argon (IG01). It is a noble gas that occurs naturally in the atmosphere; its GWP and ODP are zero, and it leaves no chemical residue. It is our preferred solution in large volumes and in facilities where environmental priority is at the highest level.
These recommendations are not a rule but a starting point: the final selection is clarified on a project basis according to the space’s volume, space constraints, occupancy and environmental priority. FM200 remains a valid option when the most compact storage is required.
The central (banked) system advantage
Gas suppression can be installed with two architectures: a modular system that places separate cylinders in each space, or a central (banked) system in which a single cylinder bank protects multiple spaces. In multi-room facilities the advantages of the central system are clear:
- Fewer cylinders — Since a fire is expected in only one space at a time, a single bank protects many rooms via selector (directional) valves; the total number of cylinders and the cost drop.
- Single-point maintenance — Because all cylinders are gathered in a single pump/cylinder room, weighing, pressure checks and periodic maintenance are carried out from one point.
- Reclaimed room space — There are no cylinders in the protected rooms; valuable technical area is left for equipment.
- Scalability — When a new space is added, instead of installing an entire system it is enough to add a selector valve and nozzle line to the existing bank.
The central system is the engineering choice that lowers both investment and operating cost, especially for data centers housing numerous panel, server and UPS rooms.
Design engineering: the gas in the right place, at the right time
As important as the agent and the architecture is the correct calculation and integration of the system:
- Concentration and NOAEL calculation — The gas quantity and the design concentration are calculated so as to achieve extinguishing without exceeding the human safety threshold (NOAEL) (TS ISO 14520 / EN 15004 / NFPA 2001).
- Pipe length and distance limit — Each agent has a limited pipe length and elevation difference over which it can be carried to the nozzle; this is verified by hydraulic calculation. Whereas this distance is more restricted with low-pressure chemical gases, inert gases stored at 200–300 bar high pressure can carry the gas over much longer distances. This allows inert gases, in a central (banked) system, to protect even distant spaces spread over a large area from a single bank — a decisive advantage in large facilities.
- Discharge and hold time — Chemical gases discharge in ≈10 seconds; but what really matters is that the gas holds at the extinguishing concentration for a sufficient time (typically ≈10 minutes), otherwise a deep-seated fire may re-ignite.
- Door-fan (room-tightness) test — The room’s gas hold time is measured and verified with the door-fan test. In a leaky space the design may be correct on paper, yet extinguishing fails.
- Cross-zone scenario — To prevent false discharge, verification by two separate detectors (cross-zone), followed by delay/abort time, HVAC and damper shutdown, gas/electricity cut-off and evacuation alarm is set up in a single automated scenario.
- Cylinder bank and nozzle layout — For homogeneous distribution, the manifold and nozzle line are engineered according to the geometry of the space.
How the hazard class is determined: three classes and the high-hazard conditions
The first step of every gas-suppression design is to determine the enclosure’s hazard class, because the design concentration (C) used in the volume calculation depends on it. This classification is agent-independent — the same rules apply whichever agent is chosen; only the concentration values for each class differ by agent (those values are given in the relevant agent article). ISO 14520 defines the design concentration by applying a safety factor (×1.3) to the experimentally measured extinguishing concentration, and uses three hazard classes. NFPA 2001’s “Class C” (energized electrical) is not a separate class in ISO 14520; it is handled within Class A – High hazard.
- Class A – Surface: solid combustibles (paper, wood, plastic, textile, cable insulation) burning at the surface — the primary application of clean agents. De-energized, low cable-load spaces (archive/paper store, small electrical room) fall here.
- Class A – High hazard: spaces with dense fuel load (cable bundles, filled cable trays) or where equipment remains energized during extinguishment. Most modern technical spaces with energized equipment fall here.
- Class B – Flammable liquid: flammable/combustible liquid fire; requires the highest concentration (generator, oil-filled transformer, solvent store).
When is a space considered “Class A – High hazard”?
ISO 14520-1 clause 7.5.1.3 (aligned with NFPA 2001-2012 A.5.4.2.2) states that a space must be treated as Class A – High hazard if any of the following conditions is present:
| # | Condition |
|---|---|
| 1 | Cable bundle diameter > 100 mm (4 in) |
| 2 | Cable tray fill > 20% of cross-section |
| 3 | Spacing between horizontal/vertical cable tray layers < 250 mm (10 in) |
| 4 | Equipment that stays energized during extinguishment with total power > 5 kW |
The first three point to dense cable load, the fourth to energized equipment. The critical, often-overlooked point: a clean agent is chosen precisely to protect running (energized) equipment without shutting it down. So in a data center, server room or telecom/MDF room the equipment stays energized throughout extinguishment and the total load almost always exceeds 5 kW — meaning condition 4 is met by default. This is exactly what NFPA 2001 calls “Class C”; the result is that these spaces are treated in practice as Class A – High hazard, not Surface. Dense cabling under raised floors also brings the first three conditions into play. Note: clean agents target surface fires; true deep-seated fires that have penetrated the material mass are outside clean-agent scope and require solutions such as CO₂.
Which space falls into which class?
| Space | Class |
|---|---|
| Server / data center, telecom, MDF room | Class A – High hazard (energized, load > 5 kW) |
| Control / SCADA room | Usually Class A – High hazard; small/low-load rooms Surface |
| Cable gallery / cable basement | Class A – High hazard (dense cable) |
| Switchgear / UPS — energized (> 5 kW) or densely cabled | Class A – High hazard |
| Electrical / switchgear room — de-energized, low cable load | Class A – Surface |
| Archive, records room | Class A – Surface |
| Generator / fuel pump room | Class B |
| Oil-filled transformer, turbine enclosure | Class B (mineral oil) |
| Paint / solvent / flammable chemical store | Class B |
If a space has more than one fuel type, the design follows the most demanding class. Class determination is therefore also the first step of agent selection.
Shared calculation rules: net volume and altitude correction
Whichever agent is used (FM200, NOVEC 1230 or IG-01 argon), two calculation rules are common; they are not repeated in the agent-specific articles — this section is the source.
What may be deducted from the volume? Only permanent (non-removable) structural products — impermeable, fixed structural elements such as reinforced-concrete columns and beams — may be deducted from the gross volume. The volume of movable equipment such as cabinets, panels, server racks, shelving and machinery is not deducted, because if it is later removed the free volume grows, the gas stays the same, and the concentration drops below the design value, leaving the system deficient. The calculation is always based on the largest (safest) free volume, as if the equipment were not there.
Altitude above sea level (atmospheric correction). The volume formulas give the agent mass for sea-level atmospheric pressure (1.013 bar). TS ISO 14520-1 (clause 7.7) requires the correction only when ambient pressure deviates more than 11% from sea level — i.e. for elevation changes above roughly 1,000 m. Up to ≈1,000 m the factor is 1.00; above that the agent mass is multiplied by the Table 5 factor. The correction is agent-independent (the same factors apply to FM200, NOVEC and IG-01):
| Altitude | Correction factor |
|---|---|
| −1,000 m | 1.130 |
| 0 (sea level) | 1.000 |
| 1,000 m | 0.885 |
| 1,500 m | 0.830 |
| 2,000 m | 0.785 |
| 2,500 m | 0.735 |
| 3,000 m | 0.690 |
For example, in Ankara (≈900 m) no correction applies; at a facility 1,500 m high the agent mass is multiplied by 0.830.
Shared equipment and automation: manometer, pressure switch, damper control
Regardless of the agent, the core logic of the system’s supervisory equipment and ventilation/damper automation is identical; it is not repeated in the agent-specific articles, and this section is the source. (Only the discharge time — ≤10 s for halocarbons, ≤60 s for IG-01 argon — and the size of the pressure-relief damper — markedly larger for inert gas — vary by agent; those are covered in the relevant agent article.)
Contact-output manometer (pressure-gauge supervisory switch) — mounted on the cylinder. It continuously monitors the agent’s storage pressure; if pressure falls below the permitted threshold (leak, valve seepage or agent loss) its electrical contact closes and sends a fault/warning signal to the fire panel. Its job is not to extinguish but to verify that the system is full and ready to discharge, giving early notice of a silent agent loss.
Pressure switch — on the discharge/manifold line. When the gas actually discharges it senses the flow pressure and produces a “gas discharged” confirmation to the panel; this signal triggers the “GAS RELEASED” warning signs, HVAC shutdown and damper closure. In short, the manometer answers “is the system ready?” and the pressure switch “has the gas discharged?”
Ventilation and damper control — the correct sequence. The most common cause of failure in gas suppression is ventilation left open; if HVAC runs during discharge or dampers stay open, the gas is carried out and the hold time cannot be maintained. The correct sequence: (1) cross-zone detection, (2) alarm + delay (pre-discharge delay, evacuation), (3) stop HVAC + close all supply/exhaust/recirculation dampers before discharge, (4) discharge, (5) keep closed throughout the hold time (typically ≈10 min). The sudden room overpressure at the moment of discharge is balanced by a separate overpressure relief damper that opens momentarily only under excess pressure and re-closes — it is not a continuously open ventilation damper. After hold time and extinguishing confirmation, the space is cleared with a separate purge ventilation before re-entry.
Summary
In gas suppression, success is the correct convergence of three decisions: the right agent, the right pressure/architecture design and the right scenario integration. As A-Pro, we recommend NOVEC 1230 among chemical gases and pure argon among inert gases; in multi-space facilities we evaluate the cost and maintenance advantage of the central system. For data centers, the field where this solution is most intensively applied, you can read our Data Center Fire Safety article, and you can reach us for facility-specific agent selection and engineering with a free site survey within Ankara.
This content is for informational purposes only. A binding, facility-specific assessment requires project-based work with a fire engineer.
© 2026 A-Pro Mühendislik. This is original technical content produced by A-Pro Engineering; all rights reserved. Copying, reproducing or republishing it in whole or in part without attribution and permission is prohibited.
Frequently asked questions
How does gas suppression put out a fire?+
There are two distinct mechanisms. Chemical clean agents (FM200, NOVEC 1230) extinguish mainly by absorbing heat and partly by breaking the combustion chain. Inert gases (argon, nitrogen) act by diluting the oxygen in the space to a level at which combustion can no longer be sustained (≈12.5% with argon). Neither leaves residue nor damages electronic equipment.
Which gas suppression agent does A-Pro recommend?+
Among chemical clean agents we recommend NOVEC 1230 (FK-5-1-12): its global warming potential (GWP ≈1) and atmospheric lifetime (≈5 days) are very low, and its human safety margin is wide. Among inert gases we recommend pure argon (IG01): it is naturally occurring, with zero GWP and ODP. The final selection is made according to the room volume, space constraints and environmental priority.
Why is pressure critical in gas suppression design?+
It is critical in two respects. Storage pressure varies by agent: chemical gases are liquefied and stored under relatively low pressure with nitrogen, whereas inert gases are held at high pressure of 200–300 bar. In addition, when the gas discharges into the room, the room pressure rises sharply; therefore the space must have a correctly sized pressure relief damper that protects the structure and integrity. This damper is mandatory especially for inert gases.
What is the advantage of a central (banked) gas suppression system?+
In a central system a single cylinder bank protects multiple spaces through selector (directional) valves. This approach provides fewer cylinders, maintenance concentrated at a single point, reclaimed room space and easy scalability; it lowers the total cost in multi-room data centers and facilities.
What is a door-fan test and why is it performed?+
The door-fan (door-fan integrity / room-tightness) test measures how long the discharged gas can remain in the room at the extinguishing concentration. A leaky space loses the gas quickly, and extinguishing fails or re-ignition occurs. This test verifies the hold time and is an integral part of TS ISO 14520 / EN 15004 / NFPA 2001 design.
Related systems
Let’s discuss the right solution for your facility
Contact our engineers for a free site survey and quote within Ankara.