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INERGEN is a blend of inert atmospheric gases that contains 52% nitrogen, 40% argon, 8% carbon dioxide, used for fire suppression system agent. It is considered a clean agent for use in gaseous fire suppression applications. Inergen does not contain halocarbons, and has no ozone depletion potential. It is non-toxic. Inergen is used at design concentrations of 35-50% to lower the concentration of oxygen to a point that cannot support combustion, but still safe for humans.
Inergen has replaced the use of CO2 in fixed firefighting applications due to the dangers associated with lack of oxygen following activation of a CO2 system. The name is a portmanteau of the name of the lead engineer on the project, Dr Innes R. Geneson (and assisted by Dr Alan Steele).
A component of Inergen is carbon dioxide, which allows the human body to adapt to the environment of reduced oxygen that is present after discharge of agent. Discharge of Inergen results in an approximate 2% concentration of carbon dioxide within the space. This directs the human body to take deeper breaths and to make more efficient use of the available oxygen.
The nitrogen and argon components offset the weight of the carbon dioxide, which allows the Inergen blend to have the same density as normal atmosphere. This eliminates the need for special considerations to prevent agent leakage.
Since Inergen is composed of natural components that exist in the air – Nitrogen, Argon and Carbon Dioxide – its components simply resume their normal role in the earth’s life cycle following a discharge, so Inergen presents no environmental impact.
Many other agents break down in the combustion process forming by-products that are corrosive to electronic components and cards. Inergen does not form any corrosive by-products.
Inergen is discharged into the protected area in a “single phase” so there is no thermal shock or large temperature drop associated with the discharge. Discharge tests conducted demonstrate that the temperature drop is typically less than 2°C in room temperature.
Inergen exists in a “single phase” throughout the discharge process, that is cylinder storage, pipework distribution and nozzle discharge. This single-phase situation simplifies pipework design and computer software design (pipe friction losses etc.). Inergen is stored at high pressure (200 bar) so this allows for long pipe runs, remote cylinder location, and the option of storing the cylinders horizontally.
In addition to this extinguishing feature, people are still able to function normally in the atmosphere into which Inergen has been injected. This is attributed to the increased carbon dioxide level, which typically increases to between 2.5% to 5% of the room volume.
This increased level of carbon dioxide stimulates the rate of respiration and increases the body’s oxygen use efficiency. This compensates for the lower oxygen levels that are present when a fire is being extinguished.
As a result, the brain continues to receive the same amount of oxygen in an Inergen atmosphere as it would in a normal atmosphere, even if the oxygen concentration falls to below 10%. Hence Inergen can be used in automatic total flooding systems in areas that are normally occupied.
The physiology of breathing in a reduced oxygen-increased carbon dioxide environment has been understood since the 1930s and the Inergen respiratory concept has been approved by Occupational Health and Safety organisations Worldwide.
People can breathe within a correctly designed Inergen atmosphere without any long-term ill effects. Inergen is non toxic, so it has been possible for the agent to be medically tested on people in both Europe and the USA. This is not true for Halocarbon based products, which are all lethal at high concentrations and still toxic even at low concentrations, hence tests on these agents have been limited to laboratory animals.
Exiting during an Inergen discharge situation is made safer as the agent does not fog the atmosphere and no impairment of vision occurs.
- Inergen contains no halocarbons. It has no ozone depletion potential, and unlike halocarbon agents, it will not produce toxic or corrosive decomposition. Inergen and Argonite has the same potent suppressing effect.
- Based on an acute hypoxia point of view, Inergen is comparatively safer than any other inert gas based extinguishing agents in applications where evacuation may not be possible prior to the application of the agent.
- Inergen systems reduce oxygen concentration only enough to suppress combustion while stimulating breathing efficiency to a disproportional advantage (as with any other suppression system, human evacuation is always recommended).
- Inergen is non-toxic, and does not threaten the health compared to Halon-based or halocarbon agents.
- Inergen has almost the same density as normal atmospheric air. No particular support or precautions are needed should agent leakage occur.
- Normal in gas suppression is the "fogging effect", and because Inergen creates no 'fog' during discharge, escape routes during fire are still visible.
- Unlike carbon dioxide or halocarbon agents, Inergen agent does not liquefy under pressure. Hence Inergen requires more space for storage tanks.