Gaseous extinguishing systems
Published: 01 January, 2006
Halon 1301 and Halon 1211 were once regarded as the ‘wonder remedy’ when they were introduced in the 1960s. They were ‘clean agents’ which did not leave any corrosive or abrasive residues after use, unlike water, dry chemicals and foams which were associated with secondary non-fire damage.
Unfortunately, the halons proved to be damaging to the ozone layer and were identified in the Montreal Protocol of 1987 as two compounds that should be used in limited amounts and only under very special and critical circumstances. In 1994 an amendment of this protocol ordered the halting of halon production.
In Europe the authorities took this a step further - since 31st of December, 2003, Halon has been prohibited in fire protection equipment and in fire extinguishers. Companies and institutions are obliged to professionally dispose of any equipment containing either Halon 1301 or Halon 1211.
In the US and Canada, the substances are still in use by many organisations, due to differences in regulations compared to the European Union. In the US the policy was to slowly replace halon-based systems instead of the abrupt decommissioning that took place in Europe. Robert T. Wickham, ex-president of Kidde Fenwall, carried out research into halon replacement for the US Environment Protection Agency in. He came to several conclusions.
“With the exception of the US Department of Defense there has not been a significant concerted effort anywhere to remove Halon 1301 systems from service and replace them with products using alternatives. Further, there is no reason to believe that this will change in the absence of some compelling reason to remove these systems,” he writes in his report.
He also points out that in the absence of directed regulatory actions, no one will feel the need to intensify research in to halon destruction. Unless there is a cost-effective alternative for halon the industry will not switch to more environmentally-friendly options. “However the American standard- NFPA 2001 - Standard on Clean Agent Fire Extinguishing Systems- is currently reviewed and made more stringent concerning the use of halon - and the amended document will be published in 2006,” Robert tells IFJ.
The standard will refer to the safety regulations in NFPA 2001 to properly purchase, design, install, test, inspect, approve, operate, and maintain engineered or pre-engineered gaseous agent fire suppression systems so they will function as intended when needed. These requirements cover both halogenated agents and inert gases.
Where is change occurring?
Robert identifies only four sectors in America that have made progress towards more environmentally-friendly alternatives. These include the essential electronics market, mobile military weapons systems, merchant shipping and the oil and gas industries.
In his report he points that owners of existing Halon 1301 systems show little incentive to remove and replace them. Some American users have a perception that halons are the most cost-effective approach, as most of the replacements are regarded as being - rightly or wrongly - more expensive and less effective than halons.
Halon users have heavily invested in updating their systems to reduce the likelihood of accidental discharges. Furthermore, recycled halon is widely available on the US market, and also there are numerous supplies of European halon, which has driven the price down. The agent is so cheap that owners find that the complete recharge of a Halon 1301 system that had discharged is more economical than the replacement of the system with another alternative.
“With the exception of the commendable work done by the US Army,” Robert continues. “The deployment of systems using Halon alternatives to retrofit applications to replace existing Halon 1301 systems is considered a rare event.”
The deployment of alternative systems in the US is generally limited to new buildings and applications. Most common are gaseous total flooding systems based on using FM 200, Inergen or watermist. Often, they are used in combination with early detection systems that permit manual intervention.
Robert says that there are many advocates for each in the end-user organisations, which would imply that those approaches are all technically defendable and commercially viable. The regulations of the last two decades have forced the industry to come up with alternatives for what was and still is one of the most effective ways of suppressing and extinguishing fires in enclosed environments.
When you require fast and efficient protection for electronically sensitive rooms occupied by humans, FM-200 is a good alternative. It was the first environmentally-acceptable replacement for Halon 1301 and has zero ozone depleting potential, a low global warming potential and a short atmospheric lifetime.
This agent is regarded as suitable for computer rooms and telecommunications rooms because of its properties: it’s a colourless gas which is stored as liquid and leaves no residue. When a fire threat is present the liquid is released into the space in the form of an electrically non-conductive vapour that does not obscure vision. Furthermore, it does not displace oxygen and has a low toxicity and is therefore (say its manufacturers) ‘ideal for spaces with human occupancy’.
Another major advantage of FM 200 is the speed of reaction; it reacts within 10 seconds of discharge and quickly extinguishes any fire.
Suitable applications: Computer areas, gas turbines, oil industry installations, telecommunications and maritime applications.
CO2 is widely regarded as an ‘old time favourite’, basically because it is cheap and effective. However the agent is toxic and contributes to global warming and should not be used for spaces containing humans or animals. It is stored under pressure as liquid and when released expands to form dry ice particles not very different from snow. Under normal temperatures, the particles transform into a vapour; when there is a fire this process takes place even faster.
The carbon-dioxide vapour chokes the combustion and the snow reduces the ambient temperature to help prevent re-ignition.
The good thing about CO2 is that is leaves no residue and is electrically non-conductive. Furthermore, it is a three-dimensional agent capable of penetrating inside boxes containing electronics and fills up the whole space. It can work under high or low pressures depending on the application and it is usually installed where water would otherwise cause significant damage.
Suitable applications: Cable vaults, archives, generators, switch rooms transformer rooms, industrial processes and flammable stores
Argonite is very suitable for use within computer rooms and similar areas due to its neutral properties. It is an equal blend of two naturally-occurring inert gases, Nitrogen and Argon. It has neither ozone-depleting nor global warming potential and it is regarded by some as the most ‘environmentally acceptable’ of all gaseous extinguishing agents. Argon also complies with the NFPA 2001 Standard on Clean Agents. The agent is electrically non-conductive and leaves no residue - unlike non-brominated agents, which can produce harmful decomposition products upon contact with a flame.
When discharged into an area, the oxygen content is reduced from its ambient atmospheric level of 21% to 12% and at this reduced level fires in most flammable materials are extinguished in 30 to 45 seconds. Odorised and non-toxic for extra safety, Argonite’s effects on humans at oxygen levels of 12% and 14% are minimal and medical research has shown that there are no short or long term influences on the body. Argon has zero-toxicity and is non-ozone depletory. The substance does not fog and is perfectly clear, which ensures safe evacuation of personnel from enclosed spaces.
Suitable applications: Telecommunications, switch-rooms and computer rooms
Novec 1230 fluid is an agent with benefits and application capabilities similar to halocarbons. The difference is that Novec 1230 fluid is a fluorinated ketone, with negligible global warming potential when compared to the other halocarbon agents. It has low toxicity and has a boiling point of 48°C and therefore exists as a liquid at room temperature. It is super-pressurised with Nitrogen to 25 bar, and it rapidly extinguishes fire through a combination of heat absorption and an element of chemical interference with the flame.
The substance contains neither bromine nor chlorine and has zero ozone-depleting potential. The atmospheric lifetime of Novec 1230 is estimated to be in the range of 3-5 days and with a global warming potential of 1, it is considered that the agent has no measurable impact on climate change.
Acute toxicity testing has shown that Novec 1230 is safe for use in occupied areas. Despite having a high boiling point, Novec 1230 can be effectively vaporised over a wide range of hazard temperatures. It is therefore available to protect most hazards traditionally protected with Halon.
Suitable applications: engine rooms, maritime facilities, computer rooms, and telecom facilities
Inergen is a blend of three naturally occurring gases: Nitrogen, Argon, and Carbon-Dioxide. Is electrically non-conductive and safe for use in human-occupied facilities and will not damage sensitive electronic equipment. The substance has zero ozone depletion, zero global warming, and a zero atmospheric lifetime.
The strategy of fire extinguishment employed by an Inergen system is simple: an Inergen system lowers the oxygen content of the protected area to a point sufficient to sustain human life, but insufficient to support combustion.
Because it’s not a chemical agent, Inergen will not produce a heavy fog the way other extinguishing agents can do, so escape routes remain visible.
Suitable applications: data processing rooms, telecommunications switching facilities, process control rooms, computer rooms.