Teknik·11 min read
IG-01 Argon Inert Gas Suppression: Design Concentration, Human Safety and Volume Calculation
The engineering details that make an IG-01 argon system work: extinguishing by oxygen dilution, ISO 14520-13 design concentrations and flooding factors, the critical human-safety difference where the design concentration can exceed the NOAEL, 200/300 bar high-pressure storage and footprint, ≤60 s discharge with large pressure relief, and the agent quantity and net volume calculation.
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IG-01 is a natural inert suppression gas made of 100% pure argon. It differs fundamentally from the halocarbon clean agents (FM200, NOVEC 1230) in both its extinguishing physics and its design logic: it extinguishes not by absorbing heat but by diluting the ambient oxygen; it forms no decomposition products (HF) in the flame; and environmentally it is the most benign of clean agents (GWP = 0, ODP = 0). In return it imposes two important design constraints: high-pressure, many-cylinder storage (a large footprint) and a narrower human-safety margin than the halocarbons. We covered agent selection generally in Gas Suppression: Design and Agent Selection, and the halocarbon agents in the FM200 and NOVEC 1230 articles. Here we examine IG-01 argon from an engineering standpoint.
Suppression mechanism and discharge time
IG-01 extinguishes fire by oxygen dilution (physically). As argon fills the room, ambient oxygen falls from the normal 21%; depending on the design concentration it drops to about 10–12.5%, a level too low to sustain most fires. Because argon is a noble (inert) gas it does not decompose chemically in the flame — it forms none of the decomposition products, such as hydrogen fluoride (HF), that halocarbons produce at high temperature. It leaves no residue and does not harm electronic equipment.
Discharge time is a critical difference. The ≤10-second rule for halocarbons shortens the agent’s exposure to flame to reduce decomposition-product formation. Argon forms no decomposition products, so that constraint does not apply; for inert gases ISO 14520 / EN 15004 / NFPA 2001 require reaching 95% of design concentration within ≤60 seconds (120 s in special cases). The longer time allows both the controlled discharge of the large gas volume and management of the overpressure.
Hazard classes and design concentration (ISO 14520-13)
In Turkey, inert gas suppression design is based on TS ISO 14520-13 (IG-01) and NFPA 2001. Unlike halocarbons, the required inert gas quantity is calculated from a logarithmic flooding relationship; each design concentration corresponds to a flooding factor (kg/m³) per cubic metre. The ISO 14520-13 values for IG-01 (pure argon) at 20 °C:
| Class | Design concentration | Flooding factor (20 °C) | Remaining oxygen (approx.) |
|---|---|---|---|
| Class A — Surface | 41.9% | 0.9015 kg/m³ | ≈12.2% |
| Class A — High hazard | 48.3% | 1.0953 kg/m³ | ≈10.9% |
| Class B — Flammable liquid | 50.8% | 1.1776 kg/m³ | ≈10.3% |
- Class A – Surface: surface burning of solid combustibles (paper, wood, plastic, cable insulation); de-energised, low-cable-load spaces (archives, small electrical rooms).
- Class A – High hazard: enclosures with a dense fuel load or where equipment stays energised during discharge.
- Class B – Flammable liquid: heptane (cup-burner) basis; generator/fuel room, oil-filled transformer.
Which class a space falls into — the definitions of the three classes, the four high-hazard conditions of ISO 14520-1 clause 7.5.1.3 (cable bundle >100 mm · tray fill >20% · tray stacks <250 mm apart · energised >5 kW) and the “which space, which class” table — is agent-independent; for the detail, see the hazard-class determination section of our Gas Suppression: Design and Agent Selection article. In brief: energised data center/server/telecom rooms meet condition 4 (energised + >5 kW) by default and are therefore treated in practice as Class A – High hazard (48.3%); the Surface (41.9%) value is for de-energised, low-cable-load spaces.
Human safety: NOAEL/LOAEL and IG-01’s critical difference
This is the most important design difference between IG-01 and the halocarbons. The physiological thresholds for argon (tied to oxygen level):
- NOAEL 43% (remaining oxygen ≈12%)
- LOAEL 52% (remaining oxygen ≈10%)
- LTC 62% (remaining oxygen ≈8%)
The comparison is striking. In NOVEC 1230 the design concentration (5.6%) is far below the NOAEL (10%) — a wide safety margin. For IG-01, however:
- Class A – Surface (41.9%) stays just below the NOAEL (43%) → a limited margin.
- Class A – High hazard (48.3%) and Class B (50.8%) design concentrations EXCEED the NOAEL (43%) and enter the NOAEL–LOAEL band.
So in a typical high-hazard space such as a data center, the IG-01 design concentration is above the NOAEL. This does not mean IG-01 cannot be used in occupied spaces; it means exposure is time-limited: the remaining oxygen is not driven below the LOAEL level (10%), and per the EN 15004 / ISO 14520 physiological exposure-time tables a time delay, audible-visual alarm and rapid egress are mandatory. When choosing IG-01, the designer must therefore set the egress time and delay scenario far more carefully than for halocarbons.
High-pressure storage and footprint
Argon does not liquefy at room temperature; it is stored as a single-phase gas, typically at 200 or 300 bar. Where liquefied gases like FM200/NOVEC fit in a few compact cylinders, IG-01 needs far more and larger cylinders to protect the same volume. Cylinder pressure varies with temperature (a 300 bar system reads ≈300 bar at 20 °C and lower when colder), so storage and enclosure temperature both enter the calculation.
The practical consequence: IG-01’s main drawback is not mass but footprint. In the example below, ≈329 kg of argon for a 300 m³ server room corresponds to roughly 8–9 cylinders of 80 L / 300 bar — where the same room is solved with a few cylinders of FM200 or NOVEC. A separate room, plus supports/wall-fixing for the cylinder bank, must be planned.
Environmental profile: GWP = 0 and permanent regulatory exemption
IG-01 is a noble gas naturally present in the atmosphere (0.93%). Its global-warming potential is zero (GWP = 0), its ozone-depletion potential is zero (ODP = 0) and the concept of “atmospheric lifetime” does not apply — it is the atmosphere itself. It is subject to no F-gas regulation and never will be. Where HFC-based FM200 has a GWP of ≈3220 and NOVEC ≈ 1, IG-01 is an absolute zero. Where environmental priority and natural composition are decisive, IG-01 is the superior clean-agent option.
Agent quantity and volume calculation
For inert gas the required argon mass is calculated with the ISO 14520 / NFPA 2001 logarithmic flooding formula:
W = (V / s) × ln[100 / (100 − C)]
- W = required argon mass (kg)
- V = protected net free volume (m³)
- C = design concentration (%)
- s = specific volume of argon (m³/kg); at 20 °C ≈ 0.602 m³/kg (density ≈ 1.66 kg/m³), increasing with temperature
In practice the table values are used: W = V × flooding factor. The flooding factor is the simplified form of the formula at 20 °C (e.g. 1.0953 kg/m³ for 48.3%).
Example: a server room of 100 m² floor area and 3.0 m height (V = 300 m³), T = 20 °C. Because the equipment stays energised during discharge the space is Class A – High hazard; C = 48.3% is used:
W = 300 × 1.0953 ≈ ≈329 kg of argon
Formula check: s = 0.602 m³/kg; W = (300 / 0.602) × ln(100 / 51.7) = 498 × 0.660 ≈ 329 kg.
Note that this mass requires ≈8–9 cylinders of 80 L / 300 bar. For comparison, the same room needs ≈203 kg and a few cylinders of FM200 (high hazard 8.5%) and ≈248 kg of NOVEC (5.6%). IG-01 demands both more mass and markedly more cylinders/space; its advantage is not mass economy but the environmental profile and the absence of decomposition products. As temperature falls the argon density rises and more mass is needed for the same volume, so the enclosure’s lowest design temperature is used.
Altitude above sea level and the atmospheric correction
The correction is agent-independent and applies only above ≈1,000 m (TS ISO 14520-1 cl. 7.7); the agent mass is multiplied by the Table 5 factor. For example, the room above draws no correction in Ankara (≈900 m, ≈329 kg); at a facility 1,500 m high it becomes 329 × 0.830 ≈ ≈273 kg. For the full factor table and rationale, see the shared calculation rules in our Gas Suppression: Design and Agent Selection article.
What may — and may not — be deducted from the volume?
Only permanent structural elements (reinforced-concrete columns/beams) may be deducted from the gross volume; movable equipment such as cabinets, panels and server racks is not deducted — if removed, the free volume grows and the concentration drops below the design value. The calculation is always based on the largest (safest) free volume. For detail, see the shared calculation rules in our pillar article.
Nozzle layout and height
The maximum area per nozzle depends on the approval listing, and the two approval schemes differ markedly. Under a VdS-approved system a single nozzle protects about ≈30 m², whereas under UL/FM-approved systems (NFPA 2001 / UL 2127 / FM 5600) the area is much larger — for example, with Viking OXEO PR LCP argon nozzles, 8.0 × 8.0 m (≈64 m²) for the VN TFI 360° and 10.6 × 10.6 m (≈112 m²) for the VN TFI 180°. In every case the value from the approval listing of the actual nozzle used is applied. Layout rules:
- Nozzles are placed in the upper part of the protected volume/void; up to 5 m a single level is enough.
- For enclosures taller than 5 m, additional nozzle levels are added to achieve the design concentration throughout the volume.
- If raised-floor and suspended-ceiling voids are protected, a separate nozzle is placed at each level, and those volumes are added to the agent quantity.
Pressure relief: critical and large for inert gas
In inert gas suppression a large gas volume is added to the room (the flooding factor is roughly 42–51% of the room volume in argon). This creates a much higher overpressure at discharge than with halocarbons. The pressure-relief vent (damper) is therefore mandatory for IG-01 and markedly larger; correct cross-section sizing is critical so the enclosure fabric (walls, glazing, doors) is not damaged. The damper opens momentarily at discharge to relieve the overpressure, then closes for the hold time.
System devices and damper automation
The core logic of the contact-output pressure gauge, the pressure switch and the ventilation/damper automation is common to all gas systems; for the detail and the correct discharge sequence, see the shared equipment and automation section of our Gas Suppression: Design and Agent Selection article. In brief: the pressure gauge monitors cylinder pressure and verifies the system is ready to fire; the pressure switch senses discharge and triggers the alarm/HVAC shutdown/damper closure; the dampers are closed before discharge and kept closed throughout the hold time.
IG-01-specific points: discharge completes in ≤60 seconds (unlike the ≤10 s limit for halocarbons); given the high cylinder pressure, gauge supervision is especially critical; the evacuation/delay step is applied rigorously for human safety (the design concentration exceeds the NOAEL); and the pressure-relief damper is sized large, as described above. After the hold time, the purge exhausts residual gas and returns oxygen to normal.
Design and installation checklist
- Class determination: energised data center/server/telecom spaces are treated as Class A – High hazard (48.3%); the surface value (41.9%) is for de-energised, low-cable-load spaces.
- Human safety and time: the high-hazard and Class B design concentrations exceed the NOAEL (43%); apply time delay, rapid egress and the EN 15004/ISO 14520 exposure-time limits rigorously.
- Footprint: plan a separate room, supports and fixing for the 200/300 bar cylinder bank; the cylinder count far exceeds that of halocarbons.
- Pressure relief: because of the large gas volume, the pressure-relief damper is large and must be sized correctly — critical for structural integrity.
- Net free volume: deduct only columns/beams; do not deduct equipment.
- Altitude correction: applied only above ≈1,000 m (TS ISO 14520 cl. 7.7); below that the factor is 1.00.
- Voids and height: include suspended-ceiling/raised-floor voids in the volume; enclosures taller than 5 m need additional nozzle levels.
- ≤60 s discharge: pipe and nozzle hydraulics are sized to achieve this.
- Tightness and door-fan test: hold time is verified by a door-fan test; cable penetrations and door undercuts are sealed.
- Periodic maintenance: cylinder pressure checks are done regularly; for detail see our periodic maintenance of fire systems article.
Summary
Success in IG-01 argon design means selecting the correct design concentration per ISO 14520-13 (Class A – Surface 41.9%, High hazard 48.3%, Class B 50.8%) and correctly managing two inert-gas realities: (1) the human-safety margin is narrower than for halocarbons — the high-hazard concentration exceeds the NOAEL, so egress and time management are critical; (2) high-pressure, many-cylinder storage brings a large footprint. IG-01’s advantage is not mass or space economy but its absolute environmental cleanliness (GWP = 0) and the absence of decomposition products. For the field where these decisions apply most intensively, see our Data Center Fire Safety article; contact us for facility-specific IG-01 design and volume calculation with a free site survey within Ankara.
This content is for information only. Binding calculation and design for your facility require project-based work with a fire engineer under TS ISO 14520-13 / NFPA 2001 and the relevant nozzle approval listing.
© 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 the IG-01 argon design concentration change with hazard class?+
The basis in Turkey, TS ISO 14520-13, defines three hazard classes for IG-01 (pure argon): Class A – Surface 41.9% (flooding factor 0.9015 kg/m³); Class A – High hazard 48.3% (1.0953 kg/m³); Class B – Flammable liquid 50.8% (1.1776 kg/m³). These concentrations reduce ambient oxygen to about 12.2%, 10.9% and 10.3% respectively. Data center/server/telecom spaces holding energised equipment satisfy the 4th high-hazard condition (energised + > 5 kW) by default, so in practice they are treated as Class A – High hazard (48.3%).
How does IG-01 argon extinguish fire?+
Unlike the halocarbon clean agents (FM200/NOVEC), IG-01 extinguishes not by absorbing heat but by diluting the ambient oxygen. The room fills with 41.9–50.8% argon and oxygen drops from 21% to about 10–12.5%, a level too low to sustain most fires. Because argon is a noble (inert) gas it does not decompose in the flame — it forms no decomposition products such as HF, a significant advantage over halocarbons.
Is IG-01 safe for occupied spaces?+
Partly, and time-limited. For IG-01 the NOAEL is 43% (oxygen 12%), the LOAEL 52% (oxygen 10%) and the LTC 62% (oxygen 8%). Class A – Surface (41.9%) stays below the NOAEL. But the Class A – High hazard (48.3%) and Class B (50.8%) design concentrations EXCEED the NOAEL (43%) and fall in the NOAEL–LOAEL band. This is the fundamental difference from halocarbons: in NOVEC 1230 the design (5.6%) is well below the NOAEL (10%), whereas for IG-01 high hazard the design is above the NOAEL. So in occupied spaces a time delay, rapid egress and the EN 15004/ISO 14520 exposure-time limits are mandatory.
Why does IG-01 require many high-pressure cylinders?+
Argon does not liquefy at room temperature; it is stored as a single-phase gas, typically at 200 or 300 bar. Where liquefied gases like FM200/NOVEC fit in a few compact cylinders, IG-01 needs far more and larger cylinders to protect the same volume. For example, ≈329 kg of argon for a 300 m³ server room corresponds to roughly 8–9 cylinders of 80 L / 300 bar. IG-01's drawback is this footprint; its advantage is the environmental profile and the absence of decomposition products.
Why is IG-01 argon discharged in ≤60 seconds?+
The ≤10-second rule for halocarbons exists to minimise the decomposition products (HF) formed when the agent contacts flame. Argon is inert and produces no decomposition products, so that constraint does not apply. For inert gases ISO 14520/EN 15004/NFPA 2001 require reaching 95% of design concentration within ≤60 seconds (120 s in special cases). The longer time allows the large gas volume to discharge in a controlled way and the overpressure to be managed.
What is the environmental profile of IG-01 argon?+
IG-01 is a noble gas naturally present in the atmosphere (0.93%); its global-warming potential is zero (GWP = 0), its ozone-depletion potential is zero (ODP = 0) and the concept of atmospheric lifetime does not apply — it is the atmosphere itself. It is not subject to any F-gas regulation and never will be. In this respect it is the environmentally superior option among clean-agent gases.
Does altitude above sea level affect the IG-01 agent quantity?+
Yes, but only at high altitude. TS ISO 14520-1 (clause 7.7) requires the atmospheric correction only when ambient pressure deviates more than 11% from sea level — roughly above 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 (1,500 m → 0.830). This correction is agent-independent; the same factors apply to IG-01, NOVEC and FM200.
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