Inert v Chemical Fire Suppression Systems

The Advantages and Disadvantages of:

Chemical Systems (FM200/NOVEC/CO2) v Inert Systems (i3/Inergen)

A Fire alarm system is used to activate the fire suppression agent.

The fire detection used in these types of fire systems are usually conventional, but as technology improves, more addressable fire alarm systems are now being used.

Chemical Systems (FM200/NOVEC/CO2)

In contrast, Chemical systems, such as FM-200 are very different.

These are manufactured chemical fire extinguishing agents, normally HFC's, which work at low concentrations and attack the fire directly at a molecular level, rather than by reducing Oxygen levels.

They are low pressure fire suppression systems, generally 25 bar, and the agent is stored as a liquid, super-pressurised with Nitrogen to "push" them along the dedicated pipe work.

 

Benefits of Chemical fire suppression Systems are:

• Discharge within 10 seconds ensuring rapid suppression of fire.
• Low storage pressure (25bar)
• The fire suppression agent is stored as a liquid, smaller footprint of hardware than Inert Gas Systems
• Do not reduce Oxygen levels
• Can be modular in design, enabling simple pipe work layout installations
• Easy to retrofit - Additional cylinders can be added, or levels "topped up" without risk of Over Pressurising the enclosure
• Zero Ozone Depletion Potential, time of depletion depends on the fire suppression agent used.

The negatives with Chemical Systems are:

• Some possibility of Global Warming
• Small possibility of breakdown of products if in direct contact with large flame
• Being low in pressure, cylinders need to be stored and installed as close to enclosure being protected as possible
• More difficult to retain within the enclosure once discharged, as agents are heavier than air

All of the fire systems, both Inert and Chemical are approved for use all over the world by bodies such as UL, FM, LPCB etc and are recognised by Environmental Agencies like the EPA as being suitable for use in normally occupied spaces.

 

Inert Systems (i3/Inergen)

These fire suppression systems, which are stored at a much higher pressure of between 150bar and 300 bar, extinguish fires in a passive manner. They reduce the Oxygen content within the protected enclosure to a point where fire can no longer survive or start.

The benefits of these inert type of system are :

• Being high pressure, they can be stored longer distances from the fire risk being protected.
• They have a very good ozone depletion potential of zero.
• They have a very low Global Warming Potential
• No possibility of breakdown products
• Discharge time is usually 60 seconds
• They can be used in different design situation and are able to be used in multi room engineered systems (many risks from one bank of cylinders)
• Similar density to air, hence easier to retain after discharge

The negatives with Inert Gas fire suppression Systems are:

• Being high pressure a higher quantity of gas is required, Also, Pressure Relief Venting will always be required to prevent potential damage to the structure of the enclosure.
• Because they are stored as a gas and not a liquid, many cylinders are required in comparison to Chemical agents
• Complicated and high pressure pipe work is required to expel the gas into the protected area.
• Method of fire extinguishment is through Oxygen Reduction
• Inert Systems cannot be modular in design and must use a central bank design system.

Fire alarm maintenance is similar for both types of fire suppression system.

The fire alarm would usually consist of a fire alarm control panel, detection, sounders, hold off button etc.

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