Inert gases in fire suppression systems are non-reactive gases used to suppress fires by reducing oxygen levels in the protected area to a point where combustion cannot be sustained. They are particularly useful in protecting sensitive areas such as data centers, museums, and laboratories where traditional water-based or chemical extinguishers could cause damage to equipment or valuable items.
Key Inert Gases Used in Fire Suppression
The most common inert gases:
• Nitrogen (N₂)
• Argon (Ar)
• Carbon Dioxide (CO₂) – though technically not inert, it’s often grouped with inert gases due to its widespread use and similar mechanism.
• Mixtures of Nitrogen and Argon – in different ratios for specific suppression requirements, often branded under names like Inergen (a blend of nitrogen, argon, and carbon dioxide).
What an Inert Gas Suppression Works:
Inert gas systems work by displacing or diluting oxygen in the area, typically reducing it to 12-15%, which is below the level required to sustain combustion but still enough for humans to breathe for a short time. This suppression method is particularly effective because:
• Non-reactive and Clean: These gases are naturally occurring and don’t leave any residue, making cleanup unnecessary.
• Environmentally Friendly: Most inert gases have minimal environmental impact, especially when compared to halon gases which were commonly used in the past but phased out due to their high ozone-depleting potential.
• Safe for Equipment and Materials: They don’t cause corrosion, short-circuiting, or other damage to sensitive electronics or artifacts.
Types of Inert Gas Systems:
Some well-known types of inert gas systems include:
• IG-100: 100% nitrogen.
• IG-01: 100% argon.
• Argonite (IG-55): 50% nitrogen and 50% argon.
• Inergen (IG-541): 52% nitrogen, 40% argon, and 8% CO₂.
Inert gas fire suppression systems are especially valued for areas where human occupancy is expected, as they maintain some breathable air, unlike CO₂-only systems, which pose a higher risk of asphyxiation.
Comparison
The differences between inert gases used in fire suppression systems mainly revolve around their properties, efficiency in reducing oxygen, and compatibility with various environments. Here’s a breakdown of the key differences among the commonly used inert gases:
1. Nitrogen (IG-100)
• Composition: 100% nitrogen.
• Mechanism: Nitrogen reduces the oxygen concentration in the protected space to below the level needed for combustion.
• Application: Typically used in areas with very high sensitivity to other gases. It has the lowest molecular weight of the inert gases, allowing it to spread quickly in a space.
• Effectiveness: Effective for most types of fires, especially Class A (combustible materials like paper and wood) and Class C (electrical) fires.
• Safety: Safe for use in areas with human occupancy as it lowers oxygen without creating additional toxic gases.
2. Argon (IG-01)
• Composition: 100% argon.
• Mechanism: Argon is heavier than nitrogen, allowing it to settle lower in the space, potentially offering better coverage in areas with a high density of equipment or storage.
• Application: Ideal for environments where equipment or artifacts are highly sensitive to chemical reactions, such as museums or laboratories.
• Effectiveness: Excellent for Class A and Class C fires, and particularly suitable for fires involving delicate materials.
• Safety: Non-toxic and non-reactive, argon is safe in occupied areas, though its heavier nature requires higher concentrations than nitrogen to achieve the same oxygen reduction.
3.  Inergen (IG-541)
• Composition: A blend of 52% nitrogen, 40% argon, and 8% carbon dioxide.
• Mechanism: Inergen effectively lowers the oxygen concentration while also adding a small amount of CO₂, which stimulates human respiration, making it safer for occupied spaces.
• Application: Suitable for occupied spaces like control rooms and data centers where people might be present during activation.
• Effectiveness: Works well across all major fire types (Class A, B, and C) and is highly regarded for its safety profile.
• Safety: Very safe for occupied areas due to the added CO₂, which helps people breathe more easily in lower oxygen levels.
4. Argonite (IG-55)
• Composition: A mixture of 50% argon and 50% nitrogen.
• Mechanism: Argonite displaces oxygen without producing harmful byproducts and is environmentally friendly.
• Application: Often used in locations with valuable equipment or where environmental concerns are a priority.
• Effectiveness: Works well for Class A and C fires.
• Safety: Safe for use in occupied spaces as it doesn’t produce toxic byproducts, though oxygen levels still need monitoring during activation.
Summary Table:
Gas Type    Composition    Best Applications    Key Characteristics    Safety in Occupied Spaces
Nitrogen (IG-100)    100% Nitrogen    Sensitive electronic equipment    Quick spread, safe, cost-effective    High
Argon (IG-01)    100% Argon    Museums, archives    Heavy, excellent for dense areas    High
Inergen (IG-541)    52% N₂, 40% Ar, 8% CO₂    Data centers, control rooms    Safe, helps with breathing in low O₂    Very High
Argonite (IG-55)    50% Ar, 50% N₂    Sensitive and eco-conscious areas    Environmentally safe, neutral byproducts    High
In summary, the main differences between inert gases in fire suppression systems involve their molecular weight, oxygen displacement efficiency, environmental safety, and suitability for occupied spaces. These differences help in selecting the best inert gas solution based on the specific needs and risks of the protected area.