Firefighting foam is a foam used for fire suppression. Its role is to cool the fire and to coat the fuel, preventing its contact with oxygen, thus achieving suppression of the combustion. Firefighting foam was invented by the Moldovan engineer and chemist Aleksandr Loran in 1902. [1]
The surfactants used must produce foam in concentrations of less than 1%. Other components of fire-retardant foams are organic solvents (e.g., trimethyl-trimethylene glycol and hexylene glycol), foam stabilizers (e.g., lauryl alcohol), and corrosion inhibitors.
Class A foams were developed in the mid-1980s for fighting wildfires. Class A foams lower the surface tension of the water, which assists in the wetting and saturation of Class A foams with water. It penetrates and extinguishes embers at depth. This aids fire suppression and can prevent re-ignition. [3] Favourable experiences led to its acceptance for fighting other types of class A fires, including structure fires. [4]
Class B foams are designed for class B fires—flammable liquids. The use of class A foam on a class B fire may yield unexpected results, as class A foams are not designed to contain the explosive vapours produced by flammable liquids. Class B foams have two major subtypes.
Synthetic foams are based on synthetic surfactants. They provide better flow and spreading over the surface of hydrocarbon-based liquids, for faster knockdown of flames. They have limited post-fire security and are toxic groundwater contaminants.
Protein foams contain natural proteins as the foaming agents. Unlike synthetic foams, protein foams are bio-degradable. They flow and spread slower, but provide a foam blanket that is more heat-resistant and more durable.
Protein foams include regular protein foam (P), fluoroprotein foam (FP) (a mixture of protein foam and fluorinated surfactants), film-forming fluoroprotein (FFFP), [6] [ full citation needed ] alcohol-resistant fluoroprotein foam (AR-FP), and alcohol-resistant film-forming fluoroprotein (AR-FFFP).
Every type of foam has its application. High-expansion foams are used when an enclosed space, such as a basement or hangar, must be quickly filled. Low-expansion foams are used on burning spills. AFFF is the best for spills of jet fuels, FFFP is better for cases where the burning fuel can form deeper pools, and AR-AFFF is suitable for burning alcohols. High-performing FFF are viable alternatives to AFFF and AFFF-AR for various applications. The most flexibility is achieved by AR-AFFF or AR-FFFP. AR-AFFF must be used in areas where gasoline is blended with oxygenates, since the alcohols prevent the formation of the film between the FFFP foam and the gasoline, breaking down the foam, and rendering the FFFP foam virtually useless.
There are 2 main application techniques [7] of applying foam onto a fire, recognized by the European (EN1568) and international (ISO7203) standards:
Sweep (roll-on) method - Use only on a pool of flammable product on open ground. Direct the foam stream onto the ground in front of the product involved. May need to move the hose line or use multiple lines to cover the material. If multiple lines are used, be aware of other firefighters in the area.
Bankshot (bankdown) method - Firefighter uses an object to deflect the foam stream so it flows down the burning surface. Application should be as gentle as possible. Direct the foam at a vertical object. Allow the foam to spread over the material and form a foam blanket.
Raindown method - Used when unable to employ the bankshot method or the roll-on method. Loft the foam stream into the air above the material and let it fall gently onto the surface. Effective as long as the foam stream completely covers the material. Might not be effective if wind conditions are unfavorable
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Water has long been a universal agent for suppressing fires, but is not best in all cases. For example, water is typically ineffective on oil fires, and can be dangerous. Fire-fighting foams were developed for extinguishing oil fires.
In 1902, a method of extinguishing flammable liquid fires by blanketing them with foam was introduced by Russian engineer and chemist Aleksandr Loran. Loran was a teacher in a school in Baku, the center of the Russian oil industry at that time. Impressed by large, difficult-to-extinguish oil fires that he had seen there, Loran tried to find a liquid substance that could deal effectively with them. He invented fire-fighting foam, which was successfully tested in experiments in 1902 and 1903. [1] In 1904 Loran patented his invention, and developed the first foam extinguisher the same year. [8]
The original foam was a mixture of two powders and water produced in a foam generator. It was called chemical foam because of the chemical action to create it. In general, the powders used were sodium bicarbonate and aluminium sulfate, with small amounts of saponin or liquorice added to stabilise the bubbles. Hand-held foam extinguishers used the same two chemicals in solution. To actuate the extinguisher, a seal was broken and the unit inverted, allowing the liquids to mix and react. Chemical foam is a stable solution of small bubbles containing carbon dioxide with lower density than oil or water, and exhibits persistence for covering flat surfaces. Because it is lighter than the burning liquid, it flows freely over the liquid surface and extinguishes the fire by a smothering (removal/prevention of oxygen) action. Chemical foam is considered obsolete today because of the many containers of powder required, even for small fires.
In the 1940s, Percy Lavon Julian developed an improved type of foam called Aerofoam. Using mechanical action, a liquid protein-based concentrate, made from soy protein, was mixed with water in either a proportioner or an aerating nozzle to form air bubbles with the free-flowing action. Its expansion ratio and ease of handling made it popular. Protein foam is easily contaminated by some flammable liquids, so care should be used so that the foam is applied only above the burning liquid. Protein foam has slow knockdown characteristics, but it is economical for post-fire security.
In the early 1950s, high-expansion foam was conceived by Herbert Eisner in England at the Safety in Mines Research Establishment (now the Health & Safety Laboratory) to fight coal mine fires. Will B. Jamison, a Pennsylvania Mining Engineer, read about the proposed foam in 1952, requested more information about the idea. He proceeded to work with the US Bureau of Mines on the idea, testing 400 formulas until a suitable compound was found. In 1964, Walter Kidde & Company (now Kidde) bought the patents for high expansion foam. [9]
In the 1960s, National Foam, Inc. developed fluoroprotein foam. Its active agent is a fluorinated surfactant that provides an oil-rejecting property to prevent contamination. In general, it is better than protein foam because its longer blanket life provides better safety when entry is required for rescue. Fluoroprotein foam has fast knockdown characteristics and it can also be used together with dry chemicals that destroy protein foam.
In the mid-1960s, the US Navy developed aqueous film-forming foam (AFFF). This synthetic foam has a low viscosity and spreads rapidly across the surface of most hydrocarbon fuels. A water film forms beneath the foam, which cools the liquid fuel, stopping the formation of flammable vapors. This provides dramatic fire knockdown, an important factor in crash rescue firefighting.
In the early 1970s, National Foam, Inc. invented alcohol-resistant AFFF technology. AR-AFFF is a synthetic foam developed for both hydrocarbon and polar-solvent materials. Polar solvents are combustible liquids that destroy conventional fire-fighting foam. These solvents extract the water contained in the foam, breaking down the foam blanket. Hence, these fuels require an alcohol- or polar-solvent-resistant foam. Alcohol-resistant foam must be bounced off of a surface and allowed to flow down and over the liquid to form its membrane, compared to standard AFFF that can be sprayed directly onto the fire.
In 1993, Pyrocool Technologies Inc. acquired the patent rights to a wetting agent with superior cooling properties that is effective on Class A, Class B, Class D as well as pressurized and 3-dimensional fires involving both hydro carbon based fuels and polar solvents such as alcohol and ethanol. The wetting agent is marketed under the name of Pyrocool. Pyrocool Technologies Inc. was awarded the 1998 Presidential Green Chemistry Award by the USEPA. Carol Browner, the USEPA Administrator in 1998, described Pyrocool as the "Technology for the Third Millennium: The Development and Commercial Introduction of an Environmentally Responsible Fire Extinguishment and Cooling Agent". A dispute with the manufacturer, Baum's Castorine, resulted in Baum's rebranding this formula under the name Novacool UEF and has been selling this product under that name since 2008.
In 2002, BIOEX a French manufacturer of firefighting foam, pioneer in environmentally friendly foams, launched the first fluorine-free foam (ECOPOL) into the market. The foam concentrate is highly efficient on class B hydrocarbon and polar solvent fires, as well as on class A fires. Their environmental challenge has been to convince their customers to choose their new generation of green products, which are 100% fluorine free, and have proven to be effective. [10]
In 2010, Orchidee International of France developed the first FFHPF, the highest performing fluorine-free foam. The foam has achieved a 97% degradability rating and is currently marketed by Orchidee International under the brand name "BluFoam". The foam is used at 3% both on hydrocarbon and polar solvent fires.
Studies have shown that PFOS is a persistent, bioaccumulative, and toxic pollutant. [11] [12] [13] It was added to Annex B of the Stockholm Convention on Persistent Organic Pollutants in May 2009. [14] Regulations in the United States, Canada, European Union, Australia, and Japan have banned the new production of PFOS-based products, including firefighting foams. [15] 3M phased out production of PFOS in 2002 due to toxicity concerns. [16]
One study, published in 2015, found that firefighters were more likely to have fluorinated surfactants in their bloodstream. [17] In 2016, the United States Air Force paid $4.3 million for a water treatment system for residents downstream of Peterson Air Force Base in Colorado. [18] [19]
In the United States, discharges of AFFF by vessels to surface waters are regulated by the United States Environmental Protection Agency (EPA) and Department of Defense, pursuant to the Clean Water Act. [20] [21]
In Australia, in 2015 a public safety announcement was issued by the New South Wales Environment Protection Authority following a water source contamination near RAAF Base Williamtown. Surface water, groundwater and fish were reported to contain chemicals from firefighting foams that had been released by the local Royal Australian Air Force base prior to training protocol changes in 2008. [22] The residents of the area were advised to not consume any bore water, in addition to eggs and seafood from fauna exposed to the contaminated water. [23] The discovery led to the banning of all forms of fishing in the waters of Fullerton Cove until the beginning of October 2016. [24] [25]
As of 2017, the Australian Department of Defence was dealing with two class action suits brought by those affected by contamination at Williamtown and at Army Aviation Centre Oakey. [26] [27] Along with many airports and fire services, the Department of Defence is investigating possible contamination at 18 military sites across Australia. [28] At Williamtown, it is also conducting studies on the uptake and residual contamination in plants, chickens and eggs. [29]
In December 2017, New Zealand's Minister for the Environment announced that higher than acceptable levels of PFOS and PFOA were found in groundwater at two Royal New Zealand Air Force bases, thought to be from historic use of firefighting foam containing the substances. [30] Residents residing near the airbases were told to drink bottled water until more extensive testing could be carried out. [31]
In 2020, state government agencies in the US are planning to dispose of firefighting foam, either by incineration or landfilling. Nearly 1 million US gal (3,800 kl) of foam will be disposed by the US. The potential health risks of incinerating AFFF are still being investigated by EPA and state agencies. [32]
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from DuPont, which originally discovered the compound in 1938. Polytetrafluoroethylene is a fluorocarbon solid, as it is a high-molecular-weight polymer consisting wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances wet PTFE, as fluorocarbons exhibit only small London dispersion forces due to the low electric polarizability of fluorine. PTFE has one of the lowest coefficients of friction of any solid.
Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often have distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Several fluorocarbons and their derivatives are commercial polymers, refrigerants, drugs, and anesthetics.
Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word "surfactant" is a blend of surface-active agent, coined in 1950. As they consist of a water-repellent and a water-attracting part, they enable water and oil to mix; they can form foam and facilitate the detachment of dirt.
Dry cleaning is any cleaning process for clothing and textiles using a solvent other than water. Clothes are instead soaked in a water-free liquid solvent. Perchloroethylene is the most commonly used solvent, although alternative solvents such as hydrocarbons, and supercritical CO2 are also used.
Perfluorooctanoic acid is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock. PFOA is considered a surfactant, or fluorosurfactant, due to its chemical structure, which consists of a perfluorinated, n-heptyl "tail group" and a carboxylic acid "head group". The head group can be described as hydrophilic while the fluorocarbon tail is both hydrophobic and lipophobic.
Halomethane compounds are derivatives of methane with one or more of the hydrogen atoms replaced with halogen atoms. Halomethanes are both naturally occurring, especially in marine environments, and human-made, most notably as refrigerants, solvents, propellants, and fumigants. Many, including the chlorofluorocarbons, have attracted wide attention because they become active when exposed to ultraviolet light found at high altitudes and destroy the Earth's protective ozone layer.
The fire triangle or combustion triangle is a simple model for understanding the necessary ingredients for most fires.
Cyclopentane (also called C pentane) is a highly flammable alicyclic hydrocarbon with chemical formula C5H10 and CAS number 287-92-3, consisting of a ring of five carbon atoms each bonded with two hydrogen atoms above and below the plane. It occurs as a colorless liquid with a petrol-like odor. Its freezing point is −94 °C and its boiling point is 49 °C. Cyclopentane is in the class of cycloalkanes, being alkanes that have one or more carbon rings. It is formed by cracking cyclohexane in the presence of alumina at a high temperature and pressure.
Organofluorine chemistry describes the chemistry of organofluorine compounds, organic compounds that contain a carbon–fluorine bond. Organofluorine compounds find diverse applications ranging from oil and water repellents to pharmaceuticals, refrigerants, and reagents in catalysis. In addition to these applications, some organofluorine compounds are pollutants because of their contributions to ozone depletion, global warming, bioaccumulation, and toxicity. The area of organofluorine chemistry often requires special techniques associated with the handling of fluorinating agents.
A compressed air foam system is used in firefighting to deliver fire retardant foam for the purpose of extinguishing a fire or protecting unburned areas.
In fire protection, an accelerant is any substance or mixture that accelerates or speeds the development and escalation of fire. Accelerants are often used to commit arson, and some accelerants may cause an explosion. Some fire investigators use the term "accelerant" to mean any substance that initiates and promotes a fire without implying intent or malice. The accelerant works by burning rapidly. As such, the accelerant itself is consumed in the process, and should not be considered as a catalyst. In Arson investigation, the significance of accelerant is to detect the presence of a such substance in order to proved that the fire is classified as an arson.
Scotchgard is a 3M brand of products, a stain repellent and durable water repellent applied to fabric, furniture, and carpets to protect them from stains. Scotchgard products typically rely on organofluorine chemicals as the main active ingredient along with petroleum distillate solvents.
Cleaning agents or hard-surface cleaners are substances used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing offensive odors, and avoiding the spread of dirt and contaminants to oneself and others. Some cleaning agents can kill bacteria and clean at the same time. Others, called degreasers, contain organic solvents to help dissolve oils and fats.
A fire extinguisher is a handheld active fire protection device usually filled with a dry or wet chemical used to extinguish or control small fires, often in emergencies. It is not intended for use on an out-of-control fire, such as one which has reached the ceiling, endangers the user, or otherwise requires the equipment, personnel, resources or expertise of a fire brigade. Typically, a fire extinguisher consists of a hand-held cylindrical pressure vessel containing an agent that can be discharged to extinguish a fire. Fire extinguishers manufactured with non-cylindrical pressure vessels also exist but are less common.
Perfluorononanoic acid, or PFNA, is a synthetic perfluorinated carboxylic acid and fluorosurfactant that is also an environmental contaminant found in people and wildlife along with PFOS and PFOA.
Per- and polyfluoroalkyl substances are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain; there are 7 million such chemicals according to PubChem. PFAS came into use after the invention of Teflon in 1938 to make fluoropolymer coatings and products that resist heat, oil, stains, grease, and water. They are now used in products including waterproof fabric such as Nylon, yoga pants, carpets, shampoo, feminine hygiene products, mobile phone screens, wall paint, furniture, adhesives, food packaging, heat-resistant non-stick cooking surfaces such as Teflon, firefighting foam, and the insulation of electrical wire. PFAS are also used by the cosmetic industry in most cosmetics and personal care products, including lipstick, eye liner, mascara, foundation, concealer, lip balm, blush, and nail polish.
A perfluorinated compound (PFC) or perfluoro compound is an organofluorine compound that lacks C-H bonds. Many perfluorinated compounds have properties that are quite different from their C-H containing analogues. Common functional groups in PFCs are OH, CO2H, chlorine, O, and SO3H. Electrofluorination is the predominant method for PFC production. Due to their chemical stability, some of these perfluorinated compounds bioaccumulate.
Perfluorooctanesulfonyl fluoride (POSF) is a synthetic perfluorinated compound with a sulfonyl fluoride functional group. It is used to make perfluorooctanesulfonic acid (PFOS) and PFOS-based compounds. These compounds have a variety of industrial and consumer uses, but POSF-derived substances ultimately degrade to form PFOS.
Fluorine may interact with biological systems in the form of fluorine-containing compounds. Though elemental fluorine (F2) is very rare in everyday life, fluorine-containing compounds such as fluorite occur naturally as minerals. Naturally occurring organofluorine compounds are extremely rare. Man-made fluoride compounds are common and are used in medicines, pesticides, and materials. Twenty percent of all commercialized pharmaceuticals contain fluorine, including Lipitor and Prozac. In many contexts, fluorine-containing compounds are harmless or even beneficial to living organisms; in others, they are toxic.
This timeline of events related to per- and polyfluoroalkyl substances (PFASs) includes events related to the discovery, development, manufacture, marketing, uses, concerns, litigation, regulation, and legislation, involving the human-made PFASs. The timeline focuses on some perfluorinated compounds, particularly perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) and on the companies that manufactured and marketed them, mainly DuPont and 3M. An example of PFAS is the fluorinated polymer polytetrafluoroethylene (PTFE), which has been produced and marketed by DuPont under its trademark Teflon. GenX chemicals and perfluorobutanesulfonic acid (PFBS) are organofluorine chemicals used as a replacement for PFOA and PFOS.