What gases are used in fire suppression systems?
Not all fire suppression systems use gas to put out fires, but many do. Unlike water, powder, or foam fire suppression systems, gas suppression systems can put out fires without damaging equipment. Some gaseous fire suppression systems do not require any clean up at all after they put out a fire.
There are several different kinds of gases that can be used to suppress a fire. Some of the most common gases used in fire suppression systems are:
- Carbon dioxide (CO2)
- Clean agents, including HFC-227ea (FM200) and FK-5-1-12 (Novec 1230)
- Inert Gases, including Inergen
We will discuss the properties, advantages, and disadvantages of each type of gaseous fire suppression system.
Clean Agent Fire Suppression Systems
Both HFC-227ea and FK-5-1-12 are types of clean agent fire suppression systems. Clean agents are commonly used to suppress fires in machinery and electrical equipment, because they do not damage components. Clean agents can also be used to protect occupied spaces, such as electrical rooms, because they are safe for people.
Clean agents are also safe for the environment; they do not cause ozone depletion and they have minimal global warming potential compared to alternatives.
HFC-227ea is one type of clean agent. The original manufacturer of HFC-227ea is Chemours, who sell the chemical under the brand name FM200. This clean agent functions by removing heat, which puts out a fire. HFC-227ea can also disrupt free radicals, which can help extinguish a fire by interfering with key chemical reactions.
HFC-227ea is a heptaflouropropane, which is a type of heptaflourocarbon (HFC). Although there are some environmental concerns with HFC’s, fire suppression systems are largely exempt from legislation that bans the use of HFC’s. That’s because fire suppression systems only contain a small amount of HFC’s and do not discharge them into the atmosphere frequently enough to cause significant environmental harm.
FK-5-1-12 is another type of clean agent. The original manufactuer of FK-5-1-12 is 3M, who sell the chemical under the brand name Novec 1230. Until 2020, 3M had patent on FK-5-1-12, but the patent expires on July 31, 2020. Like HFC-227ea, FK-5-1-12 suppresses fires by removing heat.
Unlike HFC-227ea, FK-5-1-12 is a fluorinated ketone. Because FK-5-1-12 is not an HFC, it is generally considered more environmentally friendly. When it comes to environmental impact, the key difference between the two chemicals is their global warming potential (GWP). Novec 1230 has a lower global warming potential than FM200.
Carbon Dioxide (CO2) Fire Suppression Systems
Carbon dioxide is another commonly used gas in fire suppression systems. Like clean agents, carbon dioxide does not require clean up after discharge. Unlike clean agents, carbon dioxide puts out fires by removing oxygen, not heat. This is a critical difference, because it means that carbon dioxide can not be used in occupied spaces. Because carbon dioxide removes oxygen, it can suffocate people. If you are using a carbon dioxide system for fire suppression, make sure to completely ventilate the area if the system goes off. Only then is it safe for personnel to assess the damage.
We advise against using carbon dioxide for protection of electronic equipment due to the risk of thermal shock. Thermal shock occurs because carbon dioxide can be stored at extremely cold temperatures. When the carbon dioxide discharges, it can freeze electronic components, causing irreversible damage. Clean agents are a better choice for protection of electrical cabinets and other similar equipment.
In spite of its limitations, carbon dioxide has several key advantages. Notably, it is both readily available and cost effective. In other words, if a system discharges, it is easy to get it refilled at a reasonable price. Therefore, carbon dioxide may be a good choice if you believe your equipment could have multiple fires during its service life. This is often the case with EDM machines, which can be protected with a high-pressure CO2 system.
Inert Gas Fire Suppression Systems
Inert gases function in a similar way to carbon dioxide: by removing enough oxygen to prevent combustion (or fire). However, unlike carbon dioxide, inert gases are considered safe to use in occupied spaces, because they do not reduce oxygen enough to pose a suffocation risk. Some examples of inert gases include:
Inert gas fire suppression systems feature many of the same benefits as clean agent fire suppressions systems:
- They are safe for people
- They are safe for equipment
- They do not damage the ozone layer or contribute to global warming
So, what is the difference between inert gas fire suppression systems and clean agent fire suppression systems? While inert gases are stored as gas, clean agents are stored either as a liquid (FK-5-1-12) or as a liquified and compressed gas (HFC-227ea). The result is that clean agents can be stored in smaller containers that take up less space. However, inert gases flow better through piping, which means that they can be stored farther away from the source of a potential fire. These logistical considerations can be important during the design stages of a building or room.
Halon Fire Suppression Systems
Before clean agents and inert gases, there were halon fire suppression systems. Halon is a gas that has many of the same benefits as clean agents and inert gases. It is inert, safe for equipment, and effective at suppressing class A, B, and C fires.
However, halon has been proven to deplete the Earth’s ozone layer. As such it was banned by the Montreal Protocol in 1989. While some older fire suppression systems that are still in service may contain halon, fire suppression systems that were manufactured in the last 20 years are unlikely to contain this type of gas.