The extinguishing agent used in ProInert Fire Extinguishing System is a 50%-50% blend of Nitrogen and Argon — more commonly known by its ASHRAE designation: IG-55. Because both Nitrogen and Argon occur naturally in the atmosphere, the Ozone depleting factor is zero. The Global Warming effect is zero and the Atmospheric Lifetime is not a factor.
The agent is stored in high-pressure cylinders at a maximum pressure of 2,900 psi at 60F. When discharged, IG-55 requires little or no clean-up, making it especially attractive for use in applications where damage from other extinguishing methods would be prohibitive.
Performance
IG-55 extinguishes a fire by reducing the residual oxygen concentration to a level that will no longer support combustion. IG-55 is most effective when utilized in Total Flooding applications where the protected hazard is enclosed or for protection of equipment that is self-enclosed in order to maintain the agent concentration after discharge.
Because IG-55 does not decompose measurably when extinguishing a fire, there are no toxic or corrosive decomposition products found, other than those that may have been released due to the effects of the fire on the materials within the enclosure. A typical IG-55 Total Flood system is designed to provide a residual oxygen level of between 10% and 15% after discharge. While the residual oxygen level will not support combustion of most fires, personnel within the space will still be able to breathe normally, allowing sufficient time for egress, providing there are no harmful decomposition products from the materials affected by the fire itself.
IG-55 can be removed from the protected space by simple means of ventilation after the discharge.
Physical Properties
IG-55 is a clear, electrically non-conductive gas that when discharged leaves no residue and does not result in “fogging” of the hazard. IG-55 is relatively odorless; however, some odor may be detected after flame extinguishment due to decomposition products from the materials affected by the fire. Complete listing of physical and chemical properties of IG-55 are listed below.
Use and Limitations
ProInert Fire Extinguishing Systems must be designed and installed in accordance with the requirements outlined in the manual, and in accordance with the requirements of latest editions of NFPA 2001 and other applicable standards. Other countries and insurance organizations may have differing requirements. ProInert Fire Extinguishing Systems are used to protect hazards that are enclosed and described as Total Flooding; this provides a means to establish and maintain an effective extinguishing concentration.
Typical hazards that can be protected include the following:
- Electrical and electronic hazards.
- Telecommunications facilities.
- Storage Rooms — Flammable liquids and gases.
- Sub floors and other concealed spaces.
- High value assets, where the associated down-time would be costly.
- ProInert Fire Extinguishing Systems shall NOT be used on fires involving the following materials:
- Chemicals or mixtures of chemicals that are capable of rapid oxidation in the absence of air. Examples include Cellulose Nitrate and Gunpowder.
- Reactive metals such as Lithium, Sodium, Potassium, Magnesium, Titanium, Zirconium, Uranium, and Plutonium.
- Metal hydrides such as Sodium Hydride and Lithium Aluminum Hydride.
- Chemicals capable of undergoing auto thermal decomposition. Examples include Organic Peroxides and Hydrazine.
Exposure
Although IG-55 is composed of gases that occur naturally in the atmosphere and is considered to be non-toxic, the following guidelines have been established regarding human exposure. These guidelines are defined as follows (extracted from NFPA 2001)
- Inert gas systems designed to a concentration below 43% (corresponding to an oxygen concentration of 12%, sea level equivalent of oxygen) shall be permitted, where means are provided to limited exposure to no longer than 5 minutes.
- Inert gas systems designed to concentration between 43 and 52% (corresponding to between 12% and 10% oxygen, sea level equivalent of oxygen) shall be permitted, where means are provided to limited exposure to no longer than 3 minutes.
- Inert gas systems designed to concentration between 52 and 62% (corresponding to between 10% and 8% oxygen, sea level equivalent of oxygen) shall be permitted given the following: (a) The space is normally occupied (b) Where personnel could possibly be exposed, means are provided to limit the exposure to less than 30 seconds.
- Inert gas systems designed to concentration above 62% (corresponding to 8% oxygen or below, sea level equivalent of oxygen) shall only be used in unoccupied areas where personnel are not exposed to such oxygen depletion.
WARNING: Unnecessary exposure of personnel to the heat or by-products produced by the products affected by the fire should be avoided.
WARNING: For risks that are occupied, ensure that the system is designed such that exposure of personnel to agent concentration is within the limits specified above.
Pre-discharge alarms and time delays are intended to prevent unnecessary exposure to humans where their presence is not critical to the operation of the area being protected. Suitable safeguards shall be provided to ensure prompt evacuation of (and prevent entry into) protected areas after discharge. Safety devices, such as warning signs, audible devices, self-contained breathing apparatus, evacuation plans and personnel training shall be considered where applicable.
Pre-discharge alarms and evacuation drills shall be provided for areas where the design concentration results in a residual Oxygen level of less than 10%.
