AUTHOR: Brian O'Connor

Energy Storage System

Battery Energy Storage Hazards and Failure Modes

Around the globe energy storage systems are being installed at an unprecedented rate, and for good reasons. There are a lot of benefits that energy storage systems (ESS) can provide, but along with those benefits come some hazards that need to be considered. This blog will talk about a handful of hazards that are unique to energy storage systems as well as the failure modes that can lead to those hazards. While there are many different types of energy storage systems in existence, this blog will focus on the lithium-ion family of battery energy storage systems. The size of a battery ESS can also vary greatly but these hazards and failure modes apply to all battery ESS regardless of size. HAZARDS As with most electrical equipment there are common hazards that need to be addressed as part of operation and maintenance such as a potential for electrical shock and arc flash. These should always be accounted for when working in and around energy storage systems. More information on how to work with electrical equipment safely can be found in NFPA 70E, Standard for Electrical Safety in the Workplace. Thermal Runaway – Thermal runaway is the uncontrollable self-heating of a battery cell. It begins when the heat generated within a battery exceeds the amount of heat that can be dissipated to its surroundings. The initial overheated cell then generates flammable and toxic gasses and can reach a heat high enough to ignite those gasses. This phenomenon can cascade to adjacent cells and progress through the ESS, thus the term “runaway”. Off Gassing – The gasses that ae released from battery energy storage systems are highly flammable and toxic. The type of gas released depends on the battery chemistry involved but typically includes gases such as: carbon monoxide, carbon dioxide, hydrogen, methane, ethane, and other hydrocarbons. If the gas is able to reach it’s lower explosive limit before finding an ignition source then there is the potential for an explosion. An example of this occurred in Surprise, Arizona back in 2019. Stranded Energy – Standard energy is the term used for when a battery has no safe way of discharging its stored energy. This commonly occurs after an ESS fire has been extinguished and the battery terminals have been damaged. This is a shock hazard to those working with the damaged ESS since it still contains an unknown amount of electrical energy. Stranded energy can also lead to reignition of a fire within minute, hours, or even days after the initial event. FAILURE MODES There are several ways in which batteries can fail, often resulting in fires, explosions and/or the release of toxic gases. Thermal Abuse – Energy storage systems have a set range of temperatures in which they are designed to operate, which is usually provided by the manufacturer. If operating outside an acceptable temperature range, the ESS may not work as intended, may result in premature aging of the battery, and can even cause a complete failure that can lead to fire and explosions. Thermal abuse is caused by external sources, it is the result of contact with burning or overheated adjacent cells, elevated temperatures, or exposure to other external heat sources associated with both storage of the cells or the environment in which the ESS is installed. Electrical Abuse – Electrical abuse takes place when a battery is overcharged, charged too rapidly, or externally short-circuited. This can also occur if the battery is discharged too rapidly or if the battery is over discharged below its specified end voltage. Electrical abuse can lead to an inoperable ESS, overheating, fire, and explosion. Mechanical Abuse – Mechanical abuse occurs if the battery is physically compromised when the battery is crushed, dropped, penetrated, or otherwise distorted to failure by mechanical force. Internal Faults – Internal faults can result from inadequate design, the use of low-quality materials, or deficiencies in the manufacturing process. It might be worth noting that the failure rate for lithium-ion cells is said to be on the order of one in a million. Environmental Impacts – Environmental impacts can lead to battery failure. This can be the result of ambient temperature extremes, seismic activity, floods, ingress of debris or corrosive mists such as dust (deserts) or salt fog (marine locations), or rodent damage to wiring.  Some locations subjected to rapid temperature variations such as in the mountains can experience dewing leading to damage within the ESS located outdoors if not well-controlled. While there are numerous applications and advantages to using battery energy storage systems it is important to keep in mind that there are hazards associated with these installations. Understanding the hazards and what leads to those hazards is just the first step in protecting against them. Strategies to mitigate these hazards and failure modes can be found in NFPA 855, Standard for the installation of Energy Storage Systems. NFPA also has a number of other energy storage system resources including the following: Fact sheet on ESS PV and ESS training ESS resource page Blog on residential ESS
Man in a warehouse

Unique Fire Protection Challenges Found in Warehouse/Distribution Centers

NFPA research shows that warehouse fires happen at a frequent rate with an average of 1,410 warehouse fires, two deaths, 20 injuries, and an estimated $159.4 million in direct property damage annually. To avoid becoming part of these statistics it is essential that a fire protection system is correctly designed, installed, inspected, maintained, and tested. Warehouse environments require additional considerations for sprinkler system design. This is due to the nature of how warehouses are designed and used. This blog will look at a handful of unique fire protection challenges found in warehouses and other distribution centers. For more specific information on how to design a sprinkler system see NFPA 13, Standard for the Installation of Sprinkler Systems. Commodity classification The most obvious unique characteristic of a warehouse is that the purpose of the building is to store a large number of goods and products. This can increase the fire load by a significant amount. This is why it is essential, when designing an automatic sprinkler system for a warehouse, that the items being stored are assigned the proper commodity classification. When determining the commodity classification, it is important to include not only the product itself but also the packing material as well as the container and pallet. The different commodity classifications are as follows: Class I – a noncombustible product that is either stored in single layer cardboard boxes or shrink wrapped or paper wrapped. The product can either be stored with or without wooden pallets. Class II – A noncombustible product stored in either wooden crates or multiple-layered cardboard boxes. The product can either be stored with or without wooden pallets. Class III – A product made from wood, paper, natural fibers, or Group C plastics. This can be stored with or without wooden crates and pallets. Class IV – A product that can be made from a mixture of Group B plastics with wood, paper, natural fibers or Class C plastics. The product is allowed to be made from a small percentage of Group A Plastics Group C Plastic – Certain plastics such as PVC. This is treated the same as a Class III Commodity Group B Plastic – Certain plastic rubbers such as silicone. This is treated the same as a Class IV commodity. Group A Plastic -   The most flammable plastics and natural rubbers. This group is further subdivided into expanded or nonexpanded plastics. This is treated differently from all other commodity classifications. In rack sprinklers Warehouses are the only location where you will find sprinklers both at the ceiling level as well as in racks closer to ground level. This is a unique way to get water in the racks and applied to a fire before it is able to grow beyond the capabilities of the sprinkler system. Some higher hazard commodities will require in-rack sprinklers while other commodities have the option to include rack sprinklers and decrease the robustness of the ceiling sprinklers. Prewetting Most sprinkler systems rely on the concept of prewetting as a critical component in controlling a developing fire. Prewetting is when the sprinkler system activates and wets the fuel in front of the fires path, slowing down the fire growth. The issue with warehouses is that they can contain encapsulated products, which are impervious to prewetting (think of something that is wrapped in plastic on all sides). Due to this challenge the sprinkler system would have to be designed to be robust enough to be able to control a fire without prewetting. Obstructions In warehouses there is the potential for Early Suppression Fast Response (ESFR) sprinklers to be used. ESFR sprinklers rely on getting water to the fire quickly, this means both activating earlier than normal sprinklers and discharging water at a higher velocity. Because of this unique design feature, it makes it even more important to ensure that these sprinklers are clear of obstructions. If the sprinklers were prevented from reaching the fire during the early stages of fire growth the sprinkler could be ineffective. Change management Warehouses are likely to have items with varying commodity classifications being stored. Sprinkler design can account for this by either designing to the highest hazard commodity or by creating separate zones for higher and lower hazard commodities. Either way, when warehouses change what they are storing it is essential that the new products do not exceed the hazard level that the sprinklers were designed for. Flammable liquids and gasses Another unique fire protection challenge for warehouses is that there might be large quantities of hazardous materials such as flammable liquids and gasses. These types of materials typically fall outside of the scope of NFPA 13 and into other NFPA documents such as NFPA 30, Flammable and Combustible Liquids Code, NFPA 55, Compressed Gases and Cryogenic Fluids Code, NFPA 52, Vehicular Natural Gas Fuel Systems Code or NFPA 58, Liquified Petroleum Gas Code. These codes contain requirements on the specific containers, building construction, and/or sprinkler design required for the storage of these more hazardous materials. These are just some of the many unique fire protection challenges for warehouse and other similar distribution centers. For more information check out our Warehouse Fact Sheet. Also, come check out NFPA’s 125th Anniversary Conference series on November 16, which will feature presentations on automatic warehouse storage and retrieval systems, the importance of water supply assessment, a review of the changes to the 2022 edition of NFPA 13, and other relevant systems, storage, and suppression topics. Buybox:Title:Featured training|OLS1322SPR

Transformer Fire Protection

While superheroes and the big box office may have everything thinking about robots when we talk about transformers, they are actually a much more important device that is essential for the transmission, distribution, and utilization of alternating current electric power. What are transformers and what do they do? In basic terms a transformer is a device that transfers electric energy from one AC circuit to another, either increasing or reducing the voltage. This is done for several reasons, but two main purposes are to reduce the voltage of conventional power circuits to operate low-voltage devices and to raise the voltage from electric generators so that electric power can be transmitted over long distances. They have been in use for a long time and are an essential piece of our electrical infrastructure. The most common transformer that people often see are located on telephone poles. Why are transformers hazardous? Transformers are often times filled with oil for insulation, to prevent electrical arcing and to serve as a coolant. This oil is similar to mineral oil and very flammable. When a transformer fails it can lead to an intense fire and violent explosion (feel free to check out one of the many videos online on exploding transformers). Transformers can hold anywhere between a few gallons to thousands of gallons. Transformers can be installed indoors or outdoors, but indoor transformers typically are not filled with oil while outdoor transformers often are. Oil insulated transformer protection methods Some of the main considerations when talking about transformer fire protection are fire walls & separation, water based fire protection systems, containment, drainage and lightning protection. Fire Wall & Separation Ideally, we want to prevent transformers from catching fire, but in the event one does catch fire or explode we want to limit the damage and potential spread of fire. This can be done by several means, the most common being physical separation and fire walls. NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations,  recommends that transformers with more than 500 gallons (1900 L) of oil be protected by a fire wall rated for 2 hours that is extended 1ft (300 mm) vertically and 2ft (600 mm) horizontally beyond the transformer. In lieu of a fire wall, physical separation is recommended anywhere from 5 to 25 ft (1.5 to 15 m) based on the oil capacity of the transformer. Fire Protection Systems NFPA 15, Standard for Water Spray Fixed Systems for Fire Protection, contains requirement on how transformers should be protected using a water spray system. If requires  0.25 gpm/ft2 [10.2 (L/min)/m2] of water to be discharged onto the envelope of the transformer itself and 0.15 gpm/ft2 [6.1 (L/min)/m2]  on the surrounding area for exposure protection. The water supply for such a system needs to be able to keep up with the designed flow rate of the system as well as 250 gpm (946 L/min) for a hose for the duration of 1 hour. Another important protection feature is a containment pit and drainage system to help retain any spilt transformer oil or discharge from a fixed water spray system. If a containment area is designated, then the fire wall should at least extend to the edge of that area. Since lightning is a potential ignition source for a transformer fire lightning protection should also be provided. For more information on how lightning protection works see NFPA 780, Standard for the Installation of Lightning Protection Systems. Transformer failures can be extremely dangerous but with the right precautions in place fires can be controlled to limit damage to the surrounding components, minimize plant downtime and improve survivability of plant staff. There is a lot more that goes into panning and designing a safe transformer installation, but this addresses the main concepts and ideas. For more information on fire protection recommendation for power generating plants check out NFPA 850, Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations.
Solar panels

Residential Energy Storage System Regulations

NFPA 855, Standard for the Installation of Stationary Energy Storage Systems, contains requirements for the installation of energy storage systems (ESS). An ESS system is a technology that helps supplement renewable energy sources (such as wind and solar), support the country’s electrical infrastructure, and can even provide electricity to our homes during a power failure. This technology has a lot of great applications but it also has inherent fire risks so it is important to manage  risks by taking some basic precautions. NFPA 855 covers a lot of different ESS topics but this blog will focus on some of the considerations related to installing an ESS in a residential one or two family home. The exact requirements for this topic are located in Chapter 15 of NFPA 855. What is an Energy Storage System? An energy storage system is something that can store energy so that it can be used later as electrical energy. The most popular type of ESS is a battery system and the most common battery system is lithium-ion battery. These systems can pack a lot of energy in a small envelope, that is why some of the same technology is also used in electric vehicles, power tools, and our cell phones. ESS are often installed in homes to supplement solar panels, but they can also be used to offset the price of electricity by charging when electricity is cheap and discharging when it is more expensive. Size limitations The residential chapter of NFPA 855 addresses the installation of residential ESS units between 1kwh and 20 kwh. After individual units exceed 20kWh it will be treated the same as a commercial installation and must comply with the requirements of the rest of the standard. There are also limitations on how much total energy can be stored in certain areas of a household. If you go beyond those thresholds, then you need to comply with the requirements for commercial installations. Area Maximum Stored Energy Utility closets, storage or utility spaces 40 kWh Garages and detached structures 80 kWh Exterior walls 80kWh Outdoor installations 80kWh   Location Energy storage systems can pose a potential fire risk and therefore shouldn’t be installed in certain areas of the home. NFPA 855 only permits residential ESS to be installed in the following areas: Attached garages Detached Garages On exterior walls at least 3 ft (914 mm) away from doors or windows Outdoors at least 3 ft (914 mm) away from doors or windows Utility closets Storage or utility spaces ESS can be installed in any of those locations, however if the room is unfinished, the walls and ceiling need to be protected by at least 5/8 in. (16 mm) gypsum board. Certain types of energy storage systems have the potential to discharge toxic gas during charging, discharging, and normal use. It makes sense that these types of energy storage systems are only permitted to be installed outdoors. One last location requirement has to do with vehicle impact. One way that an energy storage system can overheat and lead to a fire or explosion is if the unit itself is physically damaged by being crushed or impacted. Because of this risk, any battery systems installed in a location where they are subject to vehicle damage needs to be protected by approved barriers, usually in the form of safety bollards. No one wants bollards installed in their garage or driveway so ideally one would be able to move their system out of reach from vehicles. This can be accomplished by either relocating the ESS to a place where vehicles can’t access or mounting it higher on the wall so vehicles can’t accidentally run into it. Fire Detection If there is an ESS in your home then interconnected smoke alarms are required to be installed throughout your house, including any garages or rooms housing ESS units. If you run into a situation where you can’t install a smoke alarm, such as an attached garage, a heat detector must be installed and be connected to the smoke alarms in the rest of the house. Electric Vehicle Use As global sales of electric vehicles seem to be exponentially growing the committee that wrote NFPA 855 thought it would be important to include requirements for houses that will use their electric vehicles as energy storage systems. There are really only two main requirements. First, any electric vehicle used to power a dwelling while parked needs to comply with the manufacturer’s instructions and NFPA 70, National Electrical Code®. Second, the use of a vehicle to power a home can’t exceed 30 days. While there are a lot of requirements for commercial energy storage systems the rules and regulations are much more relaxed for smaller systems being installed in residential one- and two-family dwellings. I hope you enjoyed this blog. ESS is certainly a hot topic. If you are interested in  ESS, please plan to attend either the Keeping Hazardous Environments Safe one-day conference on October 5th where ESS will be discussed during two industry panel discussions or the Global Trends and Research conference on November 2, where experts will discuss ESS explosion risks during a two-hour roundtable. All NFPA 125th Anniversary Conference Series sessions are available for one year after the live date, via on-demand. For related training, articles, research reports, and more check out
Train at a station

Means of Egress with NFPA 130

NFPA 130 is the Standard for Fixed Guideway Transit and Passenger Rail Systems. It contains requirements for train stations, subway stations, the trains or subway cars themselves, and the tracks or paths these vehicles travel on. While NFPA 130 covers a wide array of topics this blog is going to concentrate on the unique means of egress requirements for fixed guideway transit and passenger rail stations. Means of Egress First, what is the means of egress? In layman’s terms the means of egress is the pathway out of a building or structure that leads to a point of safety and is comprised of three parts, the exit access, exit and exit discharge.    EXIT ACCESS - The exit access is the path that leads to the exit EXIT - The exit is the portion of a means of egress that is separated from all other spaces of the building or structure by construction, location or equipment as required to provide a protected way of travel to the exit discharge. Examples include an exit door that leads directly outside, an exit staircase, exit passageways, etc. EXIT DISCHARGE - Exit discharge is that portion of a means of egress between the termination of an exit and a point of safety. In NFPA 130 the point of safety can either be the concourse or a point of safety outside of the building. In general, the station needs to comply with the means of egress requirements in NFPA 101®, Life Safety Code®, for New Assembly Occupancies except where it is modified by NFPA 130. For more information on the means of egress check out this blog! The following sections discuss those modifications. Occupant Load Determining the occupant load is needed to figure out how quickly those occupants can egress the station. To determine the occupant load we need to assume that all of the trains are simultaneously entering the station full of passengers who need to disembark and that there is a full train’s worth of people waiting on the platform to enter the train. So, the occupant load includes both the people exiting the train as well as those waiting on the platform. This will give us a worst-case scenario of having all of the trains recalled to the station at once and having to evacuate both the vehicle and station. There is also the occupant load for each platform that must be calculated in order to make sure each platform can be evacuated in a timely manner. This number is based on peak ridership numbers, which can often require an analysis be done to determine peak ridership statistics. Similar to the station occupant load, the platform occupant load needs to assume a full train has pulled into the station and drops off an entire train load while there is another train load of people waiting on the platform. Evacuation Time When looking at evacuation times there are two main figures that must be considered. The first is the platform evacuation time which is required to be less than 4 minutes. The second is the station evacuation time, in which the occupant load needs to be able to reach a point of safety in under 6 minutes.  Travel Distance There are also limitations on travel distances and common paths of travel for platforms. Travel distance is your natural path of travel measured from the most remote point on the platform to the where the means of egress path leaves the platform. NFPA 130 requires that the travel distance is 100m (325ft) or less. There is also the concept of a common path of travel which is measured in the same manner as travel distance but terminates at that point where two separate and distinct routes become available. The common path of travel is not allowed to exceed 25m (82ft) or one car length, whichever is greater. Platforms Corridors & Ramps Many of the requirements for platforms, corridors and ramps are summarized in the table below. In addition to those limitations, when calculating available egress capacity on platforms, corridors, and ramps, 12 inches must be subtracted from each wall and 18 inches subtracted from the platform edge.   Capacity Travel Speed Minimum width Platforms 2.08 p/in.- min (0.0819 p/mm-min) 124 ft/min (37.7 m/min)   44 in. (1120 mm) Corridors 2.08 p/in.- min (0.0819 p/mm-min) 124 ft/min (37.7 m/min)   44 in. (1120 mm) Ramps 2.08 p/in.- min (0.0819 p/mm-min) 124 ft/min (37.7 m/min)   44 in. (1120 mm) Concourse   200 ft/min (61.0 m/min)   Stairs   48 ft/min (14.6 m/min)* 44 in. (1120 mm) Escalators 1.41 p/in.-min (0.0555 p/mm-min) 48 ft/min (14.6 m/min)*   Elevators carrying capacity for 30 minutes     *Travel Speed for vertical component of travel Escalators NFPA 101 typically doesn’t allow escalators to be used as a component in the required means of egress but because of the short evacuation timeframe, NFPA 130 allows it. When determining egress capacity for escalators there are a few rules that need to be followed. One escalator at each level must be assumed to be out of service and escalators cannot account for more than 50% of the egress capacity for a level unless they meet additional criteria. Elevators Elevators are another unique component of the means of egress that is allowed to be used in fixed guideway and passenger rail stations, but they also come with additional rules. One elevator must be considered out of service, elevators can’t account for more than 50% of the egress capacity and one elevator must be reserved for the fire service. The capacity of elevators is determined by calculating the carrying capacity over a 30-minute timeframe. Elevators also must meet certain construction requirements and they need to be accessed through holding areas or lobbies. Exit Hatches Exit hatches are another unique component of the means of egress permitted for fixed guideway and passenger rail stations. Exit hatches must be manually opened from the egress side with only one releasing operation requiring less than 30lb (130N) of force and have a hold-open device. It also needs to be clearly marked on the discharge side to prevent blockage. Fare Barriers Fare barriers are typically gate type or turnstile type, each of which have additional requirements that must be met to be allowed in the means of egress. Fare barriers are a unique characteristic of a station and have unique requirements. For a fare barrier to be allowed in the means of egress it must either be designed to release in the direction of travel during an emergency or be able to open by providing 15lbf (66N) of force in the egress direction. Platform Edge Provisions Finally, the platform edge is another unique feature of a station. Guards are not required along the trainway side of the platform edge. Certain horizontal sliding platform screens or doors are permitted to separate the platform from the trainway, but the doors or screens must open with less than 50 lb (220N) of force at any stopping position of the train and it needs to be able to withstand the positive and negative pressures caused by the passing trains. There are many unique fire and life safety elements found in Fixed Guideway Transit and Passenger Rail Systems. This blog discussed some of the unique means of egress characteristics, but NFPA 101 contains many more requirements that must be followed. 
Fire extinguisher on the wall

Fire Extinguisher Types

In the hands of a trained person, portable fire extinguishers are great tools to protect people and property from fire during early stages. When using an extinguisher or selecting an extinguisher to install, it’s important to know the characteristics of different fire extinguishers. This blog will address the different types of fire extinguishers by breaking them down by their extinguishing agent, which is the material inside the extinguisher that gets applied to the fire. Class of Fire Description Class A Fires Fires in ordinary combustible materials, such as wood, cloth, paper, rubber, and many plastics. Class B Fires Fires in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases. Class C Fires Fires that involve energized electrical equipment. Class D Fires Fires in combustible metals, such as magnesium, titanium, zirconium, sodium, lithium, and potassium. Class K Fires Fires in cooking appliances that involve combustible cooking media (vegetable or animal oils and fats). Water Water is the primary liquid used in these extinguishers, although sometimes other additives are also included. A drawback for pure water fire extinguishers is that it is not suitable for use in freezing conditions since the water inside will freeze and render the extinguisher unusable. Certain types of water fire extinguishers contain antifreeze which will allow the extinguisher to be used in freezing conditions. Water type fire extinguishers can also sometimes contain wetting agents which are designed to help increase its effectiveness against fire. These extinguishers are intended primarily for use on Class A fires.  Water mist extinguishers are a type of water fire extinguisher that uses distilled water and discharges it as a fine spray instead of a solid stream. Water mist extinguishers are used where contaminants in unregulated water sources can cause excessive damage to personnel or equipment. Typical applications include operating rooms, museums, and book collections. Film-forming foam type AFFF (aqueous film-forming foam) and FFFP (film-forming fluoroprotein) fire extinguishers are rated for use on both Class A and Class B fires. As the name implies, they discharge a foam material rather than a liquid or powder. They are not suitable for use in freezing temperatures. An advantage of this type of extinguisher when used on Class B flammable liquid fires of appreciable depth is the ability of the agent to float on and secure the liquid surface, which helps to prevent reignition. Carbon Dioxide type The principal advantage of Carbon Dioxide (CO2) fire extinguishers is that the agent does not leave a residue after use. This can be a significant factor where protection is needed for delicate and costly electronic equipment. Other typical applications are food preparation areas, laboratories, and printing or duplicating areas. Carbon dioxide extinguishers are listed for use on Class B and Class C fires. Because the agent is discharged in the form of a gas/snow cloud, it has a relatively short range of 3 ft to 8 ft (1 m to 2.4 m). This type of fire extinguisher is not recommended for outdoor use where windy conditions prevail or for indoor use in locations that are subject to strong air currents, because the agent can rapidly dissipate and prevent extinguishment. The concentration needed for fire extinguishment reduces the amount of oxygen in the vicinity of the fire and should be used with caution when discharged in confined spaces. Halogenated agent types Halon The bromochlorodifluoromethane (Halon 1211) fire extinguisher has an agent that is similar to carbon dioxide in that it is suitable for cold weather installation and leaves no residue. It is important to note that the production of Halon has been phased out because of the environmental damage it causes to the earth’s ozone.  Some larger models of Halon 1211 fire extinguishers are listed for use on Class A as well as Class B and Class C fires. Compared to carbon dioxide on a weight-of-agent basis, bromochlorodifluoromethane (Halon 1211) is at least twice as effective. When discharged, the agent is in the combined form of a gas/mist with about twice the range of carbon dioxide. To some extent, windy conditions or strong air currents could make extinguishment difficult by causing the rapid dispersal of the agent. Halon Alternative Clean Agents There are several clean agents that are similar to halon agents in that they are nonconductive, noncorrosive, and evaporate after use, leaving no residue. Larger models of these fire extinguishers are listed for Class A as well as Class B and Class C fires, which makes them quite suitable for use on fires in electronic equipment. When discharged, these agents are in the combined form of a gas/mist or a liquid, which rapidly evaporates after discharge with about twice the range of carbon dioxide. To some extent, windy conditions or strong air currents could make extinguishing difficult by causing a rapid dispersal of agent. Clean agent type extinguishers don’t have a detrimental effect on the earth’s ozone so these are more widely available than Halon type extinguishers. Dry chemical types Ordinary Dry Chemical The fire extinguishing agent used in these devices is a powder composed of very small particulates. Types of agents available include sodium bicarbonate base and potassium bicarbonate base. Dry chemical type extinguishers have special treatments that ensure proper flow capabilities by providing resistance to packing and moisture absorption (caking). Multipurpose Dry Chemical Fire extinguishers of this type contain an ammonium phosphate base agent. Multipurpose agents are used in exactly the same manner as ordinary dry chemical agents on Class B fires. For use on Class A fires, the multipurpose agent has the additional characteristic of softening and sticking when in contact with hot surfaces. In this way, it adheres to burning materials and forms a coating that smothers and isolates the fuel from air. The agent itself has little cooling effect, and, because of its surface coating characteristic, it cannot penetrate below the burning surface. For this reason, extinguishment of deep-seated fires might not be accomplished unless the agent is discharged below the surface or the material is broken apart and spread out. Wet chemical The extinguishing agent can be comprised of, but is not limited to, solutions of water and potassium acetate, potassium carbonate, potassium citrate, or a combination of these chemicals (which are conductors of electricity). The liquid agent typically has a pH of 9.0 or less. On Class A fires, the agent works as a coolant. On Class K fires (cooking oil fires), the agent forms a foam blanket to prevent reignition. The water content of the agent aids in cooling and reducing the temperature of the hot oils and fats below their autoignition point. The agent, when discharged as a fine spray directly at cooking appliances, reduces the possibility of splashing hot grease and does not present a shock hazard to the operator. Wet chemical extinguishers also offer improved visibility during firefighting as well as minimizing cleanup afterward. Dry powder types These fire extinguishers and agents are intended for use on Class D fires and specific metals, following special techniques and manufacturer’s recommendations for use. The extinguishing agent can be applied from a fire extinguisher or by scoop and shovel. Using a scoop or shovel is often referred to as a hand propelled fire extinguisher. Conclusion & resources While there are many different types of fire extinguishers used for different applications it is also important to know the rating of each extinguisher which will let you know the types of fires it is meant to be applied to. For more information on portable fire extinguishers take a look at the following blogs, as well as our portable fire extinguisher fact sheet. Related blogs Guide to Extinguisher ITM Guide to Extinguisher Placement

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