Gas Suppression Systems (sometimes referred to as Full Flood Systems), are an ideal way of protecting rooms (including enclosed voids) from fire, whilst ensuring limited damage to the effected room should the system activate. Water based systems will suppress any fire that starts within the room, but the unfortunate drawback is that water will have to be used. This may cause issues with technology/electrical equipment that may be in the room, not to mention damage to the fabric of the room and possible “run-through” if the room is not located on the ground floor of a building.
Gas Suppression Systems on the other hand, get around this problem by discharging a gas into the room instead of water, which considerably reduces the chances of room damage – it is just as effective and also reduces post discharge clean-up. Getting the room back into active service after an activation is also substantially quicker.
The gas is stored (sometimes locally and sometimes remotely) in pressurised cylinders for the protected space and has steel (usually galvanised) discharge pipework installed in the room to discharge the gas if required.
It is very important that the suppressant gas is discharged into the room space and also any floor voids and ceiling voids to make sure that any concealed spaces are also covered – in fact the regulations insist on this.
How Does Gas Suppression Work?
Dependent on the Gas used, Gas Suppression can be used in two different ways – the idea is to disrupt the “Fire Triangle” and stop combustion from happening.
Gas Fire Suppression System Types
The two types of gas fire suppression systems are inert gas suppression and chemical agent gas suppression.
1. Inert Gas Fire Suppression System
The first way of suppressing fires is using Inert Gas Suppression (using gases like Argonite, Argon, Inergen, and Nitrogen). This disrupts the “Fire Triangle” by reducing the Oxygen available for combustion and therefore makes combustion extremely difficult.
Here at TENX ENGINEERS, we design Inert Gas Suppression to reduce the Oxygen level from a normal 20.9 % to between 10% and 11%. At this level, combustion is next to impossible.
The air is perfectly safe to breathe, in fact it is regularly compared with being in an aeroplane at 15,000 ft. All the same, you really shouldn’t be in the space when the system goes off due to the nasties that may be given off by the fire.
The gas is held in the room for a minimum hold time of 10 minutes, which will prevent re-ignition of any fire source.
2. Chemical Agent Gas Suppression
The second method of suppressing fires is to use Chemical Agent Gas Suppression (FK 5-1-12 NOVEC 1230®, HFC227ea FM200, FE13 etc.). This disrupts the “Fire Triangle” by removing the heat from the source which again makes combustion next to impossible. The requirement for Chemical agents by volume in a room is much lower than Inert Systems, but the Oxygen level stays at 20.9%.
Again the air is perfectly safe to breathe, but the same applies about nasties given off in a fire.
The gas is held in the room for a minimum hold time of 10 minutes, which will prevent re-ignition of any fire source.
Hold Time
Every Gas Suppressed Room has a hold time associated with it which should be checked by Room Integrity Testing at least annually. By regulation, most systems should have a hold time of at least 10 minutes.
The strength of any Gas Suppression System is the enclosure that it discharges into – think of water in a fish tank. If there are huge cracks in the tank, then the water will not be in there for very long.
When gas is discharged into a room, it will initially suppress any fire in there, however, for the fire to continue to be suppressed, the gas must be held in the room. Of course, no room can be completely sealed gas-tight, however the room should be sealed well enough to hold the gas for at least 10 minutes, preferably longer.
Controlling the Gas Suppression System
The gas cylinders and pipework are mechanical and cannot work alone, they need a Fire Detection System to be able to sense a fire and signal the suppressant gas to actually discharge.
TENX ENGINEERS do this using a “Double Knock” or “Coincidence” wired system that uses multiple smoke detectors to accurately detect a fire. BS 6266 states that there must be at least 4 smoke detectors in each void and our control system looks for a smoke activation from at least two out of the four detectors.
On the detection of smoke by the first detector, the control system will go into “1st Stage Alarm”. This is a pre-alarm condition that provides warning that there may be a fire present in the room. TENX ENGINEERS use Voice Sounders to accurately tell the inhabitants of the room what is happening – gone are the days of staff having to recognise which sound relates to which stage the system is in. The Voice Sounder will sound “First Stage Extinguishant Release Warning”.
On the detection of smoke by a second detector, the control system will then confirm that there is a fire present in the room, and at this point the system control panel will start a timed countdown (normally 30 seconds) to the discharge of the suppressant gas. The Voice Sounder message will change to “Extinguishant Gas Release Imminent”.
When the timed countdown reaches zero, the gas discharge will start. This will continue for up to 2 minutes on Inert Gas Systems and 10 seconds for Chemical Agent Gas Systems (these timings are set out in BSEN15004 and also in the equipment manufacturer’s guidelines).
Room Integrity Testing
The successful performance of a gaseous total flooding system is largely dependent on the integrity of the protected enclosure. It is essential that a room integrity test is performed on any protected enclosure to establish the total equivalent leakage area and enable a prediction to be made of the enclosure’s ability to retain NOVEC. The required retention time will depend on the particulars of the hazard, but MSC/Circ.848 states that this should not be less than 15 minutes. Longer retention times may sometimes by necessary if enclosures contain hazards that may readily become deep seated.
- FM200(HFC 227ea)
- Novec1230 / FK 5-1-12
- CO2
- Inert Gases (Argon, Nitrogen, Carbon)
- Kitchen Hood Fire Suppression
- Fire Alarm System, PAVA system
- Emergency & Exit light System
- Fire Fighting System
- Fire Suppression System
- Room Integrity Test
- Fire Suppression Hydrostatic Test
- Kitchen Hood System
