Introduction: CO2, FM200, and IG100 all flood an electrical room with gas, but they store agent differently, leave different residues, and create very different life-safety conditions.
An electrical room is a small, sealed, expensive space. It holds switchgear, transformers, drives, and cable terminations that water will destroy, so designers look at gaseous suppression early. The three names that come up most often are CO2, FM200, and IG100, and they are often discussed as if they were interchangeable choices on the same shelf. They are not. They store agent at different pressures, act on a fire in different ways, and set very different conditions for anyone who might be inside the room when the system discharges.
CO2 is stored as a liquefied gas under its own vapour pressure, and that single fact explains most of its hardware. A 70L cylinder charged with 42kg of CO2 holds roughly 0.6kg of agent per litre of water capacity, and at 20°C the pressure inside that cylinder sits at around 5.7MPa. Because the cylinder carries a high fill ratio and the liquid expands as it warms, the design pressure climbs with temperature — the same cylinder is built around 12.4MPa at 50°C. High-pressure gas storage and handling at this level is a well-established industrial discipline, which is why CO2 cylinders, valves, and manifolds are engineered and tested as pressure equipment rather than as simple containers. On discharge, the liquid flashes to gas, drops sharply in temperature, and moves fast; total flooding CO2 systems are typically designed to deliver the agent within about 60 seconds. FM200 and IG100 take different storage routes. FM200 is also a liquefied gas in the cylinder, but it has a much lower vapour pressure of its own, so the cylinder is super-pressurised with dry nitrogen to push the agent through the piping. FM200 systems are commonly built around a 4.2MPa or 5.6MPa charge pressure, and the agent is typically delivered in about ten seconds. IG100 is different again: it is pure nitrogen, stored as a compressed gas rather than a liquid, in cylinders rated around 15MPa. Because none of the agent is liquid, the cylinder count per protected room is higher, and the pipe sizes and nozzle counts are larger. IG100 delivery is normally designed over a longer window, closer to a minute, which is why the room has to hold its gas long enough for the design concentration to do its work.
All three agents leave the room without residue, so the practical difference is how they suppress. FM200 interrupts the combustion chain chemically, which is why it works at design concentrations in the high single digits for electrical hazards and does not have to starve the room of oxygen. CO2 and IG100 both work mainly by dilution, but at very different levels. IG100 pushes oxygen down to roughly 12 to 13 percent, an atmosphere that requires careful evacuation planning for anyone in the space. CO2 has to hold a much higher concentration because the gas itself is doing the work, and total flooding designs commonly sit at 34 percent and above. For scale, CDC NIOSH lists 40,000ppm, or 4 percent CO2, as immediately dangerous to life or health, so a CO2 design concentration sits far above any exposure level a person can tolerate. Residue is usually the first thing buyers ask about, and here the three media are close: none of them leaves powder, foam, or water behind. What differs is the condition of the room after a discharge. A CO2 or IG100 release pushes a large volume of gas into a sealed space and then out through the openings, and the moving gas can lift dust and loose material. FM200 discharge forms a visible vapour cloud that clears with ventilation. In every case, cleanup is really about ventilation, resetting detectors, and confirming the equipment still runs, not about wiping down surfaces. Occupancy is the harder question. An electrical room may be empty most of the week, but it is never truly vacant: electricians, inspectors, and switching crews go in. FM200 can be engineered around occupied spaces with alarms, signage, and a discharge delay. IG100 needs the same alarms and also assumes the space can be cleared before oxygen drops. CO2 carries the most restrictive life-safety conditions of the three: pre-discharge alarms, a delay, discharge lockouts, and a clear rule about who may be inside while the system is armed — which in practice usually means an interlocked or normally unmanned room.
Once storage, discharge, and safety are on the table, the design conversation usually settles into four areas. They are worth separating because each one drives a different part of the room layout, the cylinder storage area, the pipe routing, and the safety strategy.
Each medium ends up matching a different mix of room volume, cylinder room space, occupancy pattern, and safety strategy. That is why the medium choice and the room design are normally worked out together rather than one after the other.
CO2, FM200, and IG100 are separate media with separate storage pressures, discharge behaviours, and life-safety conditions, and none of them is a drop-in replacement for the others. FM200 offers low design concentrations and a smaller cylinder footprint. IG100 offers a clean inert gas discharge with a larger hardware package. CO2 offers a compact high-pressure liquid supply with a fast, residue-free release and the strictest occupancy rules of the three. Electrical room decisions usually come down to room volume, available cylinder space, how often people enter the room, and what safety interlocks the project can support. Getting the medium right at design stage is far cheaper than changing it after the pipework is installed.
A：CO2 is stored as a high-pressure liquid and works mainly by oxygen displacement at design concentrations of 34 percent and above, so it carries the strictest life-safety rules. FM200 is a liquefied clean agent that suppresses chemically at much lower concentrations and is easier to design around occupied spaces. IG100 is compressed nitrogen that also dilutes oxygen, but the agent volume is large, so it needs more cylinders, bigger pipework, and full evacuation planning.
A：CO2 extinguishes by pushing oxygen out of the room, and the concentration needed to hold a fire down is far above what a person can breathe. CDC NIOSH lists 40,000ppm as immediately dangerous to life or health, while CO2 total flooding designs commonly run at 34 percent or higher. That is why CO2 rooms need pre-discharge alarms, a release delay, discharge lockouts, and a firm rule that the space is clear before the agent is released.
A：CO2 is held as a liquefied gas close to its own vapour pressure, which is why a 70L cylinder charged with 42kg sits at around 5.7MPa at 20°C and is built around 12.4MPa at 50°C. FM200 is also liquefied but has a much lower vapour pressure, so it is super-pressurised with nitrogen to a lower charge pressure. IG100 is not liquefied at all — it is compressed nitrogen stored in high-pressure cylinders near 15MPa.
Substitutes in Total Flooding Agents | US EPA
CDC - NIOSH Pocket Guide to Chemical Hazards - Carbon dioxide
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