fire retardant

A fire retardant is a substance other than water that reduces flammability of fuels or delays their combustion.[1] This typically refers to chemical retardants[2] but may also include substances that work by physical action, such as cooling the fuels; examples of these includefire-fighting foams and fire-retardant gels. The name fire retardant may also be applied to substances used to coat an object,[3] such as a spray retardant to prevent Christmas trees from burning.[4] Fire retardants are commonly used in fire fighting.Home fires damage about 400,000 homes, and cause just under 7 billion US dollars in direct damage annually in the United States.[5] Because of the importance of prevention, fire retardation has become a very notable industry.How retardants workIn general, fire retardants reduce the flammability of materials by either blocking the fire physically or by initiating a chemical reaction that stops the fire.[edit] PhysicalThere are several ways in which the combustion process can be retarded by physical action:∙By cooling: Some chemical reactions actually cool the material down.∙By forming a protective layer that prevents the underlying material from igniting.∙By dilution: Some retardants release water and/or carbon dioxide while burning. This may dilute the radicals in the flame enough for it to go out.One commonly used fire retardant coating is aluminium hydroxide. When heated, it dehydrates to form aluminum oxide (alumina, Al2O3), releasing water vapor in the process. This reaction absorbs a great deal of heat, cooling the material over which it is coated. Additionally, the residue of alumina forms a protective layer on the material's surface.[edit] Chemical action∙Reactions in the gas phase: chemical reactions in the flame (i.e. gas phase) can be interrupted by fire retardants. Generally, these retardants are organic halides (haloalkanes) such as Halon and PhostrEx. However, there are situations where the released gas might be more dangerous when this type of retardant is involved.∙Reaction in the solid phase: some retardants break down polymers so they melt and flow away from the flame. Although this allows some materials to pass certain flammability tests, there is argument over if the fire safety is truly improved by the production of flammable plastic droplets.∙Char Formation: For carbon-based fuels, solid phase flame retardants cause a layer of carbonaceous char to form on the fuel surface. This char layer is much harder to burn and prevents further burning.[6][7]∙Intumescents: These types of retardant materials add chemicals which cause swelling up behind the protective char layer, providing much better insulation behind the protectivebarrier. In additions to being added to plastics, these are available as paints for protecting wooden buildings or steel structures.[edit] UsesA Fire extinguisher[edit] Fire extinguishersClass A foam is used as a fire retardant in 2.5 gallon [APW] and [CAFS] extinguishers to contain incipient brush fires and grass fires by creating a fire break. Other chemical retardants are capable of rendering class A material and Class B fuels non-flammable and extinguishing class A, class B, and some class D fires.[citation needed] Fire retardant slurries dropped from aircraft are normally applied ahead of a wildfire to prevent ignition, while fire suppression agents are used to extinguish fires.[edit] Surface coatingIt is possible to coat an object with a fire retardant. The classic example of this is the green Christmas tree. As a tree dries out it can be accidentally lit on fire putting the home at risk. A coating of a specialised fire retardant can prevent the starting of the fire and slow it down if it does start.In addition many large sky-scrapers use a coating around main structural elements to prevent catastrophic weakening during a fire. It is believed that one of the reasons why the twintowers collapsed on 9/11 was due to the airplane impact removing portions of the fire-insulation layer.[citation needed]Many dormitories across the nation are also considering using these products. Since 2000, 109 people have died in fires in dormitories or off-campus student housing across the nation, according to Campus Firewatch, an online newsletter.Campus Firewatch's publisher, Ed Comeau, said a January 2000 fire at Seton Hall University in New Jersey drew attention to the perils of fire on campus. A common area in a Seton Hall dorm caught fire after two students ignited a banner from a bulletin board. The fire quickly spread to furniture and killed three students and injured 58 others.[8][edit] Forest-fire fightingA MAFFS-equipped Air National GuardC-130 Hercules drops fire retardant on wildfires in Southern CaliforniaRed-dyed line of fire retardant stands out clearly on this Arizona hill. Drop was against the Alambre Fire.Early fire retardants were mixtures of water and thickening agents, and later included borates[9] and ammonium phosphates.[citation needed]Generally, fire retardants are dropped from aircraft or applied by ground crews around a wildfire's edges in an effort to contain its spread. This allows ground crews time to work to extinguish the fire. However, when needed, retardant can also be dropped directly onto flames to cool the fire and reduce flame length.[10][edit] Aerial firefightingSee also: Aerial firefightingAerial firefighting is a method to combat wildfires using aircraft. The types of aircraft used include fixed-wing aircraft and helicopters. Smokejumpers and rappellers are also classified as aerial firefighters, being delivered by parachute from a variety of fixed-wing aircraft, or rappelling from helicopters. Chemicals used to fight fires may include water, water enhancers, or specially-formulated fire retardants.[11][edit] TextilesSee also: Flame Retardant and Fire Retardant FabricsMost clothing intended for children in the United States is required to pass fire-retardant tests for safety reasons.[edit] Home furnitureIn many locations mattresses are now treated with fire retardant or built with fire-resistant material. Many new foams self-extinguish. This is the most common use of fire retardancy in the chemical means.[edit] Materials[edit] Wildfire retardantsFire retardants applied to wildfires are usually a mixture of water and chemicals designed to wet the area as well as chemically retard a fire's progression through vegetation. Typically it is colored[12] so that the application area can be seen from the air. New gel-based retardants which meet NFPA Standard 1150 are being introduced into use. These are dyed other colors to differentiate them from the traditional red retardant. The gels and their dyes are designed to biodegrade naturally.[13]Phos-Chek is a brand of long-term retardant currently approved for wildland fire use.[14][edit] Environmental concernsThe examples and perspective in this section deal primarily with the United Statesand do not represent a worldwide view of the subject. Please improve this articleand discuss the issue on the talk page. (December 2010)Some fire retardants contain chemicals that are potentially dangerous to the environment, such as PBDEs. Fire retardants used in airplanes and fire resistant objects such as carpets accumulate in humans. (see PBDE#Health concerns).Forest fire retardants that are used are generally considered non-toxic,[15] but even less-toxic compounds carry some risk when organisms are exposed to large amounts.[16] Fire retardants used in firefighting can be toxic to fish and wildlife as well as firefighters[17] by releasing dioxins and furans when halogenated fire retardants are burned during fires,[18] and drops within 300 feet of bodies of water are generally prohibited unless lives or property are directly threatened.[19] The US Forest Service is the governing agency that conducts research and monitors the effect of fire retardants on wildland systems.[20][21]Fire retardant fabrics are textiles that are naturally more resistant to fire than others through chemical treatment or manufactured fireproof fibers.Terminology and test limitationsThe term fire retardant as applied to organic (i.e., containing carbon) materials, is intended to refer to reduced fire hazard, as all will burn under certain circumstances. The tests used specified in building codes, such as NFPA 701, are more correctly flame resistance tests, which test a fabric's ability to resist ignition with the flame size and duration in the test conditions.[1] The result is a comparative test, which provides a measure of the material's resistance to propagating combustion caused by small scale ignition sources. These tests do not predict the burning characteristics of full scale hazards. In many cases, if exposed to a sufficiently large and sustained exposure fire, the fire retardant fabrics will burn vigorously.[edit]Fire retardant fabrics and stage draperyFabric flammability is an important textile issue, especially for stage drapery that will be used in a public space such as a school, theatre or special event venue. In the United States, Federal regulations require that drapery fabrics used in such spaces be certified as flame or fire retardant. For draperies and other fabrics used in public places, this is known as the NFPA 701 Test, which follows standards developed by the National Fire Protection Association (NFPA). Although all fabrics will burn, some are naturally more resistant to fire than others. Those that are more flammable can have their fire resistance drastically improved by treatment with fire retardant chemicals.[edit]Fabric choices and fire retardanceStage curtain fabric choices are numerous, depending on the required style of curtain. [edit]Fire retardancy fabric treatment[edit]Durability and cleaning of fabric and drapesWhen a fabric is designated as inherently fire retardant, permanently fire retardant, or durably fire retardant, the flame retardancy will last for the life of the fabric.[citation needed] The drapery can be laundered or dry-cleaned as recommended by the drapery manufacturer.[citation needed] In the case of fabrics that are designated as fire retardant, that have been topically treated with chemicals, the flame retardancy of the fabric will dissipate over time, particularly with repeated cleaning. These fabrics must be dry-cleaned with a non-liquid cleaning agent.[citation needed] Typically, the flame retardancy of topically treated fabric is certified for one year,[citation needed] though the actual length of time in which the treatment remains effective will vary based on the number of times the drapery is dry-cleaned and the environmental conditions in the location in which the drapery is used. It is recommended that topically treated drapery be re-tested for fire retardancy on an annual basis and re-treated by a qualified professional as needed.[citation needed] This article is about chemical flame retardants used in textiles, thermoplastics and thermosets. For chemicals used to fight structure fires and wildfires, see fire retardant.Flame retardants are chemicals used in thermoplastics, thermosets, textiles and coatings that inhibit or resist the spread of fire. These can be separated into several different classes of chemicals:∙Minerals such as aluminium hydroxide ATH, magnesium hydroxide MDH, hydromagnesite, various hydrates, red phosphorus, and boron compounds, mostly borates.∙Organohalogen Compounds. These include organochlorines such as, chlorendic acid derivatives and chlorinatedparaffins; organobromines such as decabromodiphenyl ether(decaBDE), decabromodiphenyl ethane (a replacement for decaBDE), polymeric brominated compounds such as brominated polystyrenes, brominated carbonate oligomers (BCOs), brominated epoxy oligomers (BEOs), tetrabromophthalicanyhydride, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD). Most but not all halogenated flameretardants are used in conjunction with a synergist to enhance their efficiency. Antimony trioxide is widely used but other forms of antimony such as the pentoxide and sodiumantimonate are also used.Organophosphorus compounds such as organophosphates, tris(2,3-dibromopropyl) phosphate, TPP, RDP, BPADP, tri-o-cresyl phosphate, phosphonates such as DMMP and phosphinates. There is also an important class of flame retardants that contain bothphosphorus and halogen, examples of such are the chlorophosphates like TMCP and TDCP.Mineral flame retardants are typically additive while organohalogen and organophosphorus can be either reactive or additive. The basic mechanisms of flame retardancy vary depending on the specific flame retardant and the substrate. Additive and reactive flame-retardant chemicals can function in the vapor or condensed phase.The annual consumption of flame retardants is currently over 1.5 million tonnes per year, which is the equivalent of a sales volume of approx. 1.9 billion Euro (2.4 billion US-$).[1]Mechanisms of function[edit]Endothermic degradationSome compounds break down endothermically when subjected to high temperatures. Magnesium and aluminium hydroxides are an example, together with various hydrates such as hydromagnesite. The reaction removes heat from the substrate thus cooling the material. The use of hydroxides and hydrates is limited by their relatively low decomposition temperature, which limits the maximum processing temperature of the polymers (typically used in polyolefins for wire and cable applications).[edit]Thermal shieldingA way to stop spreading of the flame over the material is to create a thermal insulation barrier between the burning and unburned parts. Intumescent additives are often employed; their role is to turn the polymer into a char, which separates the flame from the material and slows the heat transfer to the unburned fuel.[edit]Dilution of gas phaseInert gases (most often carbon dioxide and water) produced by thermal degradation of some materials act as diluents of the combustible gases, lowering their partial pressures and the partial pressure of oxygen, and slowing the reaction rate.[edit]Gas phase radical quenchingChlorinated and brominated materials undergo thermal degradation and release hydrogen chloride and hydrogen bromide or if used in the presence of a synergist like antimony trioxide antimony halides. These react with the highly reactive H· and OH·radicals in the flame, resultingin an inactive molecule and a Cl· or Br· radical. The halogen radical has much lower energy than H· or OH·, and therefore has much lower potential to propagate the radical oxidation reactions of combustion.[edit]Environmental prevalenceIn 2009, the U.S. National Oceanic and Atmospheric Administration (NOAA) released a report on polybrominateddiphenyl ethers (PBDEs) and found that, in contrast to earlier reports, they were found throughout the U.S. coastal zone.[2]This nationwide survey found that New York’s Hudson Raritan Estuary had the highest overall concentrations of PBDEs, both in sediments and shellfish. Individual sites with the highest PBDE measurements were found in shellfish taken from Anaheim Bay, California, and four sites in the Hudson Raritan Estuary. Watersheds that include the Southern California Bight, Puget Sound, the central and eastern Gulf of Mexico off the Tampa-St. Petersburg, Fla. coast, and Lake Michigan waters near Chicago and Gary, Ind. also were found to have high PBDE concentrations.[edit]Health concernsFlame retardants have faced renewed attention in recent years. The earliest flame retardants, polychlorinated biphenyls (PCBs) were banned in 1977 when it was discovered that they were toxic.[3] Industries shifted to using brominated flame retardants instead, but these are now receiving closer scrutiny. The EU has banned several types of polybrominateddiphenyl ethers (PBDEs) as of 2008, 10 years after Sweden discovered that they were accumulating in breast milk.[4] As of December 2009, negotiations between EPA and the two U.S. producers of DecaBDE (a flame retardant which has been used in electronics, wire and cable insulation, textiles, automobiles and airplanes, and other applications), Albemarle Corporation and Chemtura Corporation, and the largest U.S. importer, ICL Industrial Products, Inc., resulted in commitments by these companies to phase out decaBDE for most uses in the United States by December 31, 2012, and to end all uses by the end of 2013.[5]Nearly all Americans tested have trace levels of flame retardants in their body. Recent research links some of this exposure to dust on television sets, which may have been generated from the TV heating up the flame retardants in the TV. Careless disposal of TVs and other appliances such as microwaves or old computers may greatly increase the amount of environmental contamination.[6] A recent study conducted by Harley et al. 2010[7] on pregnant women, living in a low-income, predominantly Mexican-immigrant community in California showed a significant decrease in fecundability associated with PBDE exposure in women.Another study conducted by Chevrier et al. 2010[8] measured the concentration of 10 PBDE congeners, free thyroxine (T4), total T4, and thyroid-stimulating hormone (TSH) in 270 pregnant women around the 27th week of gestation. Associations between PBDEs and free and total T4 were found to be statistically insignificant. However, authors did find a significant association amongst exposure to PBDEs and lower TSH during pregnancy, which may have implications for maternal health and fetal development.A prospective, longitudinal cohort study initiated after 11 September 2001, including 329 mothers who delivered in one of three hospitals in lower Manhattan, New York, was conducted by Herbstman et al. 2010.[9] Authors of this study analyzed 210 cord blood specimens for selected PBDE congeners and assessed neurodevelopmental effects in the children at 12–48 and 72 months of age. Results showed that children who had higher cord blood concentrations of polybrominateddiphenyl ethers (PBDEs) scored lower on tests of mental and motor development at 1–4 and 6 years of age. This was the first study to report any such associations in humans.A similar study was conducted by Roze et al. 2009[10] in Netherlands on 62 mothers and children to estimate associations between 12 Organohalogen compounds (OHCs), including polychlorinated biphenyls (PCBs) and brominated diphenyl ether (PBDE) flame retardants, measured in maternal serum during the 35th week of pregnancy and motor performance (coordination, fine motor skills), cognition (intelligence, visual perception, visuomotor integration, inhibitory control, verbal memory, and attention), and behavior scores at 5–6 years of age. Authors demonstrated for the first time that transplacental transfer of polybrominated flame retardants was associated with the development of children at school age.Another interesting study was conducted by Rose et al. 2010[11] to measure circulating PBDE levels in 100 children between 2 to 5 years of age from California. The PBDE levels according to this study, in 2- to 5-year-old California children was 10 to 1,000 fold higher than European children, 5 times higher than other U.S. children and 2 to 10 times higher than U.S. adults. They also found that diet, indoor environment and social factors influenced children’s body burden levels. Eating poultry and pork contributed to elevated body burdens for nearly all types of flame retardants. Study also found that lower maternal education was independently and significantly associated with higher levels of most flame retardant congeners in the children.San Antonio Statement on Brominated and Chlorinated Flame Retardants 2010:[12] A group of 145 prominent scientists from 22 countries signed the first-ever consensus statement documenting health hazards from flame retardant chemicals found at high levels in home furniture, electronics, insulation, and other products. This statement documents that with limited fire safety benefit, these flame retardants can cause serious health issues and as types of flame retardants are banned, the alternatives should be proven safe before being used. The group also wants to change widespread policies that require use of flame retardants.[edit]Sudden infant death syndromeMain article: Sudden infant death syndrome#Toxic_gasesUK scientist Barry Richardson claimed in 1989 that a fungus in bedding broke down the antimony, phosphorus, and arsenic flame retardants in infant bedding to form toxic gases. This research was taken up by New Zealand scientist Jim Sprott, who published a book on it, and eventually aired on The Cook Report in 1994. A 1998 UK government-sponsored study called the Limerick Report found that toxic gases were not created.[13] Based on the Limerick report, position papers publicized by US SIDS organizations[14] say there is not enough evidence to support the toxic gas theory, and that parents should continue to put their babies to sleep on vinyl-covered crib mattresses. However, Sprott maintains that his findings were not refuted.[15]。