Halocarbons in fire suppression
This paper reviews the numerous applications and installations in which the halocarbon-based clean fire suppression agents provide fire protection for sensitive and expensive mission critical assets.
Early Use Of Halocarbons In Fire Suppression
The term “halocarbons” refers to compounds containing one or more of the elements known as “halogens” – fluorine, chlorine, bromine or iodine. Halocarbons have been employed as fire extinguishing agents since the early 1900s when handheld extinguishers containing carbon tetrachloride (CCl4) were introduced. In the late 1920s methyl bromide (CH3Br) was introduced, followed in the late 1930s by bromochloromethane (CH2BrCl).
Although extremely effective fire suppression agents, the high toxicities of carbon tetrachloride, methyl bromide and bromochloromethane prompted the U.S. Army to initiate a research program to develop effective, but less toxic extinguishing agents. U.S. Army sponsored research in the late 1940s evaluated over 60 agents, and led to the development and eventual widespread use of Halon 1301 (CF3Br) in total flooding and small portable applications, and Halon 1211 (CF2BrCl) in streaming applications.
The Halons are “clean” agents, leaving no corrosive or abrasive residues following their use. As a result they are ideally suited to protect areas such as libraries and museums, where the use of water or solid extinguishing agents could cause secondary damage equal to or exceeding that caused by direct fire damage. The Halons are also non-conducting, and can be employed to protect electrical and electronic equipment. The Halons served as near ideal fire suppression agents for over 30 years. However, due to their implication in the destruction of stratospheric ozone, an amendment to the original Montreal Protocol resulted in the halting of the production of the Halons on January 1, 1994.
Research on the development of Halon replacements began in the mid to late 1980s, and involved the evaluation of thousands of compounds, by hundreds of researchers. From this extensive research the modern day “clean agents” were developed. The clean agents are comprised of two types of compounds – halocarbons and inert gases (see Table 1).
It is notable that all of the halocarbon fire suppression agents are highly fluorinated. This is due to the unique properties the fluorine atom imparts to a molecule. As the number of fluorine atoms in a molecule is increased, its toxicity and boiling point decrease, and its chemical stability and flame suppression efficiency increase – all desired properties for a total flooding extinguishing agent.
Halocarbons in modern fire suppression
Only a handful of the halocarbon clean agents listed in Table 1 have seen widespread use in total flooding applications. The iodine-containing agent CF3I – although an efficient extinguishing agent – has seen little if any practical use, due to its high toxicity and instability. The chlorine-containing agents HCFC-124 and HCFC Blend A have seen some limited use, but are slated for eventual phaseout due to their ozone depleting properties. HFC-236fa is better suited for use in streaming applications, and rarely employed as a total flooding agent.
The most widely employed clean fire extinguishing agent is HFC-227ea (FM-200), followed by the inert gas mixture IG-541 (Inergen). The halocarbon agent FK-5-1-12 (Novec 1230) is the third most widely used clean agent. These clean agents are employed for the protection of sensitive, expensive mission critical assets in applications where traditional sprinklers or other suppression systems are unsuitable. Major end use sectors include datacenters, cultural heritage facilities, military ground vehicles, military marine vessels and commercial and military aircraft.
The protection of datacenters and electronic equipment represents 95% of the worldwide clean agent market. According to a 2016 Ponemon Institute report, the average cost of datacenter downtime is nearly $9000 USD per minute – a cost of almost $216,000 USD per day of downtime. The total cost of downtime is not limited to revenue losses, but can ultimately include productivity losses, customer disruption, reputation damage, isolation and repair costs, loss of data and results, and lawsuits. The use of halocarbon clean agents allows the extinction of datacenter/electronic fires with minimal or no associated downtime. Table 2 lists a selection of major datacenters employing the halocarbon agent HFC-227ea. Noteworthy is the protection of the W.M. Keck Observatory. The Observatory is located at the summit of Hawaii’s dormant Mauna kea volcano, and houses two of the most powerful telescopes on the planet – capable of viewing 13 billion light years away.
The halocarbon clean agents leave no corrosive or abrasive residues following their use. As a result they are ideally suited to protect areas such as libraries and museums, where the use of water or solid extinguishing agents could cause secondary damage equal to or exceeding that caused by direct fire damage. Table 3 provides a selection of major cultural heritage sites protected by halocarbon clean agents.
HFC-227ea and HFC-125 are being employed in numerous military applications as seen in Table 4. The engine compartments of M2/M3 Bradley Fighting vehicles and Multiple Launch Rocket System (MLRS) vehicles have been retrofit with HFC-227ea systems, and HFC-125 systems are employed to protect the engine compartments of Stryker armored vehicles. HFC-227ea in combination with 5 weight % sodium bicarbonate (“HFC-227/BC”) is widely employed for crew compartment protection of US Army vehicles (see Table 4).
HFC-125 is employed for engine nacelle protection in various military aircraft as seen in Table 4.
Marine applications of halocarbon clean agents
The US Navy and the US Army employ both FM-200 systems and “hybrid” FM-200/water spray systems in various watercraft. These hybrid FM-200/water systems combine an FM-200 gaseous agent – for guaranteed fire extinguishment – with a low-technology water spray system operating off of a ship’s water main – to provide cooling and facilitate re-entry and ventilation. The US Army has replaced Halon 1301 systems with hybrid FM-200/water spray systems in more than sixty of their watercraft engine compartments. A small selection of military marine vessels protected by FM-200 clean agent systems are listed in Table 5.
Halocarbon clean agents are also employed in non-military marine applications. FM-200 and Novec 1230 systems are employed in the protection of pleasure craft. Internationally, numerous non-military marine vessels employ FM-200 for fire protection, as seen in Table 6.
Halocarbon clean agents are widely employed for the protection of airports (e.g., control towers, electronic control/computer rooms) and satellite installations. A selection of facilities protected by HFC-227ea systems is provided in Table 7.
New production aircraft are being installed with lavatory extinguishing (lavex) systems that contain either HFC-227ea or HFC-236fa. In addition, several airlines are replacing existing Halon 1301 lavex systems with HFC-227ea or HFC-236fa systems during scheduled maintenance operations.
Halocarbon clean agents currently protect billions of dollars worth of assets worldwide. Their clean nature renders them capable of providing fire extinguishment with minimal associated downtime and business interruption, making them an excellent choice for the protection of sensitive and expensive mission critical assets.
For more information, go to FM200.com