IG-55 (Argonite) Inert Gas Suppression System

What Is It?

IG-55, marketed as Argonite, is a carbon-dioxide-free inert gas suppression agent made of 50% nitrogen and 50% argon. Like IG-541, it works through a physical mechanism rather than a chemical reaction, lowering the ambient oxygen level in the protected space to a point where fire can no longer be sustained. Its system components — cylinder bank, manifold, discharge valves, pipe network, nozzles, control panel, and detection units — share largely the same engineering platform as IG-541 systems.

The difference between IG-55 and IG-541 is that IG-55’s blend contains no CO2. Both extinguish by diluting oxygen, and the oxygen level in the room is set by the chosen design concentration, not by the agent. The U.S. EPA lists both as acceptable under NFPA 2001, and the same concentration and exposure-time limits apply to both in occupied spaces.

How It Works

When the detection units confirm a fire, the control panel triggers the discharge valve; the gas mixture, stored as a gas at 150, 200 or 300 bar (at 15 °C), is routed through the manifold and pipe network to the nozzles and distributed through the space on the total flooding principle. In many systems a pressure-reducing device after the cylinder valve limits the pipework pressure. System components are designed for reliable operation across an ambient temperature range of -20°C to +50°C. The gas’s volumetric spread also reaches shadowed areas such as behind equipment housings and racks.

After discharge, the low-oxygen atmosphere must be held for a set hold time, which depends on the sealing level of the protected space and is verified through door-fan testing. Because discharge briefly raises the pressure in the room, a pressure relief vent suited to the room construction is also calculated.

Where It’s Used

IG-55 is used in data centers and their support areas, control and electrical rooms in industrial facilities, switchgear and equipment rooms in power plants, and technical spaces in transport infrastructure such as metro and airport facilities.

Leaving no residue and being electrically non-conductive makes IG-55 suitable for technical spaces with sensitive hardware. Local agent supply and refill options, the system manufacturer’s approvals and cylinder space usually decide between IG-55 and IG-541.

Safety

Whether IG-55 can be used in an occupied space depends on keeping the design concentration within the NFPA 2001 limits for inert gases: up to 43% concentration (about 12% oxygen) for no more than 5 minutes, 43-52% (about 12-10% oxygen) for no more than 3 minutes; higher concentrations are used only in normally unoccupied spaces. The same limits apply to IG-541.

System reliability depends on a correctly sized cylinder bank, regular pressure monitoring, and periodic room integrity testing. Making sure that anyone who might be in the space during or after discharge is alerted by the alarm, with clearly defined evacuation procedures, is an integral part of the system’s safety design.

The Inert Gas Family and Technology

IG-55 (Argonite) belongs to the inert gas family, which extinguishes by diluting oxygen. To compare IG-01, IG-100, IG-55 and IG-541 by composition, standards and density, see our inert gas fire suppression systems guide; for the technology we use in our inert gas systems, see our Fire Eater page.

This system is one of the gas fire suppression systems GYS designs and installs. Comparisons with other agents, applications and the project process are on our home page.