When it comes to fire safety, most people are familiar with the basic concept of the fire triangle and the three elements that are necessary for a fire to occur and continue burning: fuel, heat and oxygen. Based on this concept, many fire suppression technologies rely on removing one of the three elements of the fire triangle. However, there is another model that takes a more comprehensive approach to understanding fire behavior: the fire tetrahedron. While the fire triangle is a useful starting point, the fire tetrahedron provides a more nuanced understanding of the chemical reactions that take place during a fire.
In this article, we will delve into how condensed aerosol technology works by inhibiting the chemical chain reactions that sustain a fire, and how it is a highly effective and efficient solution for a wide range of applications, while caring for the environment.
Fire suppression action – how does it work?
During a fire, a chemical reaction occurs between fuel and oxygen that releases energy in the form of heat and light. As the fuel oxidizes, it releases unstable free radicals such as O2-, H+ and OH–. These free radicals act as chain carriers, initiating and sustaining the combustion process, until at least one of the elements of the fire tetrahedron is completely depleted, causing the fire to subside.
Before we can explore how condensed aerosol inhibits the chemical chain reactions at a molecular level that sustain a fire, we need to first understand what condensed aerosol is and what it’s made of.
Upon activation, the condensed aerosol-forming compound transforms from a solid state into a rapidly expanding two-phase fire suppression agent, consisting of potassium carbonate (K2CO3) – the active agent – suspended in a blend of gasses. The gas-type 3D properties of the condensed aerosol facilitate its even and fast distribution in the protected volume, as well as its flow into the natural convection currents of combustion.
In the presence of fire, the potassium-based solid particles (K2CO3) undergo thermal dissociation, forming unstable potassium free radicals (K+) which bind to the flame free radicals forming stable potassium hydroxide (KOH). KOH further reacts with CO2 and forms back stable K2CO3. The process is repeated until the fire is out. Fire suppression is thus accomplished by creating solid bonds with the free radicals and interrupting the chemical chain reactions occurring in the flame, without depleting oxygen.
The process is proven to be effective with fires involving solid, liquid and gaseous combustible materials, as well as electrical fires.
In the case of more challenging fires such as the those involving Li-ion batteries, both the active agent, K2CO3, and the intermediate product, KOH, react with the electrolyte’s decomposition products, such as hydrogen fluoride (HF), forming stable products such as potassium fluoride (KF) and potassium bifluoride (KHF2), thus preventing the formation of highly flammable gases such as hydrogen (H2). The resulting neutralizing action ultimately controls the fire and allows the temperature in the enclosure to drop below the threshold necessary (~120°C) for thermal runaway to sustain itself. Test results have shown that FirePro condensed aerosol can prevent reignition for as long as the minimum required fire-suppression density is maintained, allowing time for post-fire management of the battery.
Core components of a FirePro system
The main components of the system are the pre-engineered FirePro condensed aerosol generators, which when activated release the designed amount of fire suppression agent in the enclosure. Each generator is an all-in-one container and is the equivalent of the agent storage tank, piping and nozzles of a pressurized gas system. A complete suppression system can be configured to include single or multiple generators, depending on the physical and technical parameters of the protected area, such as the class of fire, volume and height. The quantity and model of generators to be used are determined by the agent density required, which differs from one manufacturer to another and is derived from fire suppression tests. These tests are defined in protocols set out by relevant standards such as UL2775, EN15276 or ISO15779, conducted by accredited bodies.
The FirePro range of generators fall under three main categories:
- Standard series – Suitable for Classes A, B, C & F (according to EN2 Classification) and A, B & C (according to NFPA10 Classification).
- ATEX series – The EX-certified version of the standard series, designed to suppress fires in explosive atmospheres of gas or dust mixtures (Zone 0, 1, 2 and Zone 20, 21, 22).
- HERO series – Manual generators for first responders, a tool used by trained emergency personnel such as firefighters and safety officers. The use of HERO generators buys the critical time necessary for full-scale firefighting operations.
Some key benefits of FirePro Condensed Aerosol technology:
- Non-pressurized
- Certified 15-year product life
- Can tolerate small openings in the enclosure
- Operating temperature from -54°C to +100°C
- Minimal maintenance required
- Space and weight saving
- Easy and quick to install
- No piping or nozzles required
The design, installation and maintenance of condensed aerosol fire suppression systems are governed by international and national standards, the most common standards related to the technology being NFPA 2010, EN15276, ISO15779 and IMO Circ.1270 for Sea Going Vessels under Solas74.
Condensed aerosol systems are a highly effective and versatile solution for a wide range of industries and applications as they are simple to design, without the need for complex hydraulic calculations, easy to transport and install in new or retrofit applications due to their compact size, and have a low cost of ownership during their certified product life.
Some key applications are:
- Electrical cabinets
- Electrical rooms
- Transformer rooms
- Power generator rooms
- Plant rooms
- Archives
- Warehouses
- Marine engine rooms
- Battery rooms
- Li-ion battery ESS
Environmental considerations
The condensed aerosol technology gained popularity since the ’90s due to the phase-out of Ozone depleting substances – a result of the Montreal Protocol enforced on 1 January 1989. FirePro condensed aerosol technology came to prominence in the firefighting industry in 1996 and, thanks to the use of environmentally friendly potassium salts at its core, FirePro technology is listed by the US Environmental Protection Agency (EPA) for use in normally occupied areas and as a Halon alternative under its Significant New Alternative Policy (SNAP) programme.
FirePro condensed aerosol technology is not subject to future bans as it does not contain any harmful chemical substances such as per- and polyfluoroalkyl substances (PFAs), hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) and therefore has a zero Ozone Depletion Potential (ODP), zero Global Warming Potential (GWP) and zero Atmospheric Lifetime (ALT).
Conclusion
FirePro remains committed to people and the environment and holds certificates and approvals on the most respected national and international condensed aerosol fire suppression technology standards.
With over 25 years of experience, we have succeeded in establishing a global presence from our EU headquarters, with a network of distributors covering more than 90 countries. Today, we are proud to lead the condensed aerosol fire suppression technology, and to protect lives and key assets in over 110 countries around the world.
About the Author
Dr Gianfilippi de Parenti
Dr Gianfilippi de Parenti is the Technical and Executive Director at FirePro. He has worked in the fire suppression industry for more than 30 years and has made significant contributions to the creation of international standards related to condensed aerosol technology.
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