Fire retardant

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Fire retardant dispersed aerially onto brush adjoining a firebreak to contain the Tumbleweed Fire in California, in July 2021 Tumbleweed Fire, Los Angeles County 2021, Part 9.JPG
Fire retardant dispersed aerially onto brush adjoining a firebreak to contain the Tumbleweed Fire in California, in July 2021

A fire retardant is a substance that is used to slow down or stop the spread of fire or reduce its intensity. This is commonly accomplished by chemical reactions that reduce the flammability of fuels or delay their combustion. [1] [2] Fire retardants may also cool the fuel through physical action or endothermic chemical reactions. Fire retardants are available as powder, to be mixed with water, as fire-fighting foams and fire-retardant gels.

Contents

Fire retardants are commonly used in fire fighting, where they may be applied aerially or from the ground.

Principles of operation

In general, fire retardants reduce the flammability of materials by either blocking the fire physically or by initiating a chemical reaction that stops the fire.

Physical action

There are several ways in which the combustion process can be retarded by physical action:

Commonly used fire retardant additives include mixtures of huntite (Mg3Ca(CO3)4) and hydromagnesite (Mg5(CO3)4(OH)2·4H2O), aluminium hydroxide (Al(OH)3), and magnesium hydroxide (Mg(OH)2). When heated, aluminium hydroxide dehydrates to form aluminum oxide (alumina, Al2O3, releasing water vapor in the process. This reaction absorbs a great deal of heat, cooling the material into which it is incorporated. Additionally, alumina residue forms a protective layer on the material's surface. Mixtures of huntite and hydromagnesite work in a similar manner. They endothermically decompose releasing both water and carbon dioxide, [3] [4] giving fire retardant properties [5] [6] [7] to the materials in which they are incorporated.

Chemical action

Uses

Portable fire extinguisher FireExtinguisherABC.jpg
Portable fire extinguisher

Fire extinguishers

Class 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.

Surface coating

Objects may be coated with fire retardants. For example, Christmas trees are sprayed with retardants, as a tree dries out it becomes very flammable and a fire-hazard.

Steel structures have a fire retardant coating around columns and beams to prevent structural elements from weakening during a fire.

Dormitories in the US are considering or are required by law to use these products. Intumescent coatings are used by various dormitories and in school buildings, especially those with historic structures that lack fire sprinkler systems. [10]

Forest-fire fighting

A MAFFS-equipped Air National Guard C-130 Hercules drops fire retardant on wildfires in Southern California Hercules C130 bombardier d eau Californie.jpg
A MAFFS-equipped Air National Guard C-130 Hercules drops fire retardant on wildfires in Southern California
Red-dyed line of fire retardant stands out clearly on this Arizona hill, to control the Alambre Fire Phos-check line.jpg
Red-dyed line of fire retardant stands out clearly on this Arizona hill, to control the Alambre Fire

Early fire retardants were mixtures of water and thickening agents, and later included borates [11] 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. [12]

Aerial firefighting

Aerial 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. [13]

Textiles

Materials

Wildfire retardants

Fire 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 [14] so that the application area can be seen from the air. Fire retardant gel based retardants which meet NFPA Standard 1150 are also being used in service. These are dyed other colors to differentiate them from the traditional red retardant. The gels and their dyes are designed to biodegrade naturally. [15]

A Phos-Chek tank trailer at Ramona Airport Phos-Chek Tank.JPG
A Phos-Chek tank trailer at Ramona Airport

Any fire retardant approved for use against wildfires on US Federal lands must be included on the United States Forest Service Qualified Products List. [16] To be added to that list, the product must be tested by Wildland Fire Chemical Systems, a division of the National Technology and Development Program. This process can take up to two years. [17] Phos-Chek is a brand of long-term retardant currently approved for wildland fire use. [18] Phos-Chek also has a consumer-based fire retardant spray called Wildfire Home Defense that is effective immediately after application and that remains effective until it is washed off with heavy water levels. It is designed to be applied to fuel beds around homes and outbuildings to create a firebreak in the fuels leading up to each structure. [19] Ember Bloc is another consumer-based fire retardant gel that can be applied to the exterior of one's house and nearby structures to help protect against both embers and flames in a wildfire. It has a unique ability to cling onto the side of a house to withstand high heat and windy conditions. [20]

Environmental concerns

Forest fire retardants that are used are generally considered non-toxic, [21] but even less-toxic compounds carry some risk when organisms are exposed to large amounts. [22] As of 2008, drops within 300 feet of bodies of water are generally discouraged unless lives or property are directly threatened. [23] The US Forest Service is the governing agency that conducts research and monitors the effect of fire retardants on wildland systems in the US. [24] [25]

Potential risk and health concerns

Some specialized indoor fire retardants are organic halides (haloalkanes) such as Halon and PhostrEx, which are proven to be toxic.

Studies have also shown that a drop of the retardant chemical directly into a stream may cause a sufficient ammonia concentration in the water, which is lethal to fish and other aquatic organisms. [26]

Another notable health concern is that fire-suppressant foams are especially toxic to fish in standardized soft and hard water, possibly due to surfactants. [27]

See also

Related Research Articles

<span class="mw-page-title-main">Fire</span> Rapid and hot oxidation of a material

Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. At a certain point in the combustion reaction, called the ignition point, flames are produced. The flame is the visible portion of the fire. Flames consist primarily of carbon dioxide, water vapor, oxygen and nitrogen. If hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, and any impurities outside, the color of the flame and the fire's intensity will be different.

<span class="mw-page-title-main">Aluminium hydroxide</span> Chemical compound

Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite and its three much rarer polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is amphoteric, i.e., it has both basic and acidic properties. Closely related are aluminium oxide hydroxide, AlO(OH), and aluminium oxide or alumina, the latter of which is also amphoteric. These compounds together are the major components of the aluminium ore bauxite. Aluminium hydroxide also forms a gelatinous precipitate in water.

<span class="mw-page-title-main">Magnesium hydroxide</span> Inorganic compound of formula Mg(OH)2

Magnesium hydroxide is an inorganic compound with the chemical formula Mg(OH)2. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (Ksp = 5.61×10−12). Magnesium hydroxide is a common component of antacids, such as milk of magnesia.

<span class="mw-page-title-main">Brucite</span> Magnesium hydroxide mineral

Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg(OH)2. It is a common alteration product of periclase in marble; a low-temperature hydrothermal vein mineral in metamorphosed limestones and chlorite schists; and formed during serpentinization of dunites. Brucite is often found in association with serpentine, calcite, aragonite, dolomite, magnesite, hydromagnesite, artinite, talc and chrysotile.

<span class="mw-page-title-main">Flame retardant</span> Substance applied to items to slow burning or delay ignition

Flame retardants are a diverse group of chemicals that are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings. Flame retardants are activated by the presence of an ignition source and prevent or slow the further development of flames by a variety of different physical and chemical mechanisms. They may be added as a copolymer during the polymerisation process, or later added to the polymer at a moulding or extrusion process or applied as a topical finish. Mineral flame retardants are typically additive, while organohalogen and organophosphorus compounds can be either reactive or additive.

<span class="mw-page-title-main">Fire triangle</span> Model for understanding the 3 ingredients for fires

The fire triangle or combustion triangle is a simple model for understanding the necessary ingredients for most fires.

<span class="mw-page-title-main">Aerial firefighting</span> Use of aircraft to combat wildfires

Aerial firefighting, also known as waterbombing, is the use of aircraft and other aerial resources to combat wildfires. The types of aircraft used include fixed-wing aircraft and helicopters. Smokejumpers and rappellers are also classified as aerial firefighters, delivered to the fire by parachute from a variety of fixed-wing aircraft, or rappelling from helicopters. Chemicals used to fight fires may include water, water enhancers such as foams and gels, and specially formulated fire retardants such as Phos-Chek.

This glossary of wildfire terms is a list of definitions of terms and concepts relevant to wildfires and wildland firefighting. Except where noted, terms have largely been sourced from a 1998 Fireline Handbook transcribed for a Conflict 21 counter-terrorism studies website by the Air National Guard.

<span class="mw-page-title-main">Hydromagnesite</span> Hydrated hydroxy-carbonate mineral of magnesium

Hydromagnesite is a hydrated magnesium carbonate mineral with the formula Mg5(CO3)4(OH)2·4H2O.

<span class="mw-page-title-main">Phos-Chek</span> Fire retardant

Phos-Chek is a brand of long-term fire retardants, class A foams, and gels manufactured by Perimeter Solutions, headquartered in Clayton, Missouri, United States.

<span class="mw-page-title-main">Firefighting foam</span> Foam used for fire suppression

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.

<span class="mw-page-title-main">Smouldering</span> Slow, flameless combustion

Smouldering or smoldering is the slow, flameless form of combustion, sustained by the heat evolved when oxygen directly attacks the surface of a condensed-phase fuel. Many solid materials can sustain a smouldering reaction, including coal, cellulose, wood, cotton, tobacco, cannabis, peat, plant litter, humus, synthetic foams, charring polymers including polyurethane foam and some types of dust. Common examples of smouldering phenomena are the initiation of residential fires on upholstered furniture by weak heat sources, and the persistent combustion of biomass behind the flaming front of wildfires.

<span class="mw-page-title-main">Wildfire suppression</span> Firefighting tactics used to suppress wildfires

Wildfire suppression is a range of firefighting tactics used to suppress wildfires. Firefighting efforts depend on many factors such as the available fuel, the local atmospheric conditions, the features of the terrain, and the size of the wildfire. Because of this wildfire suppression in wild land areas usually requires different techniques, equipment, and training from the more familiar structure fire fighting found in populated areas. Working in conjunction with specially designed aerial firefighting aircraft, fire engines, tools, firefighting foams, fire retardants, and using various firefighting techniques, wildfire-trained crews work to suppress flames, construct fire lines, and extinguish flames and areas of heat in order to protect resources and natural wilderness. Wildfire suppression also addresses the issues of the wildland–urban interface, where populated areas border with wild land areas.

<span class="mw-page-title-main">Combustibility and flammability</span> Ability to easily ignite in air at ambient temperatures

A combustible material is a material that can burn in air under certain conditions. A material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable material catches fire immediately on exposure to flame.

<span class="mw-page-title-main">ABC dry chemical</span> Dry extinguishing agent for firefighting

Monoammonium phosphate, ABC Dry Chemical, ABC Powder, tri-class, or multi-purpose dry chemical is a dry chemical extinguishing agent used on class A, class B, and class C fires. It uses a specially fluidized and siliconized monoammonium phosphate powder. ABC dry chemical is usually a mix of monoammonium phosphate and ammonium sulfate, the former being the active component. The mix between the two agents is usually 40–60%, 60–40%, or 90–10% depending on local standards worldwide. The USGS uses a similar mixture, called Phos Chek G75F.

<span class="mw-page-title-main">Fire retardant gel</span>

Fire-retardant gels are superabsorbent polymer slurries with a "consistency almost like petroleum jelly." Fire-retardant gels can also be slurries that are composed of a combination of water, starch, and clay. Used as fire retardants, they can be used for structure protection and in direct-attack applications against wildfires.

<span class="mw-page-title-main">Fire extinguisher</span> Active fire protection device

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.

<span class="mw-page-title-main">Ammonium polyphosphate</span> Chemical compound

Ammonium polyphosphate is an inorganic salt of polyphosphoric acid and ammonia containing both chains and possibly branching. Its chemical formula is H(NH4PO3)nOH showing that each monomer consists of an orthophosphate radical of a phosphorus atom with three oxygens and one negative charge neutralized by an ammonium cation leaving two bonds free to polymerize. In the branched cases some monomers are missing the ammonium anion and instead link to three other monomers.

<span class="mw-page-title-main">Huntite</span> Carbonate mineral

Huntite is a carbonate mineral with the chemical formula Mg3Ca(CO3)4. Huntite crystallizes in the trigonal system and typically occurs as platy crystals and powdery masses. For most of recorded history its main use was as a white pigment. Today the most common industrial use of huntite is as a natural mixture with hydromagnesite as a flame retardant or fire retardant additive for polymers.

TetraKO is a fire suppression agent marketed by EarthClean Corporation, based in South St. Paul, Minnesota. It takes the form of a white powder, which is intended to be mixed with water and sprayed on structures or foliage using unmodified firefighting equipment, up to a day in advance of a wildfire.

References

  1. ↑ "BLM Wyoming Wildland Fire Glossary". Blm.gov. 2008-06-18. Archived from the original on 2014-05-08. Retrieved 2012-08-04.
  2. ↑ Coford Glossary "Fire Retardant" Archived February 8, 2009, at the Wayback Machine
  3. ↑ Hollingbery, LA; Hull TR (2010). "The Thermal Decomposition of Huntite and Hydromagnesite - A Review". Thermochimica Acta. 509 (1–2): 1–11. doi:10.1016/j.tca.2010.06.012.
  4. ↑ Hollingbery, LA; Hull TR (2012). "The Thermal Decomposition of Natural Mixtures of Huntite and Hydromagnesite". Thermochimica Acta. 528: 45–52. doi:10.1016/j.tca.2011.11.002.
  5. ↑ Hollingbery, LA; Hull TR (2010). "The Fire Retardant Behaviour of Huntite and Hydromagnesite - A Review". Polymer Degradation and Stability. 95 (12): 2213–2225. doi:10.1016/j.polymdegradstab.2010.08.019.
  6. ↑ Hollingbery, LA; Hull TR (2012). "The Fire Retardant Effects of Huntite in Natural Mixtures with Hydromagnesite". Polymer Degradation and Stability. 97 (4): 504–512. doi:10.1016/j.polymdegradstab.2012.01.024.
  7. ↑ Hull, TR; Witkowski A; Hollingbery LA (2011). "Fire Retardant Action of Mineral Fillers". Polymer Degradation and Stability. 96 (8): 1462–1469. doi:10.1016/j.polymdegradstab.2011.05.006. S2CID   96208830.
  8. ↑ "PHOS-CHeK D75 Fire Retardants" (PDF). Archived from the original (PDF) on 2011-07-15. Retrieved 2008-11-20.
  9. ↑ "How do flame retardants work?". European Chemical Industry Council (CEFIC) and European Flame Retardants Association (EFRA). Retrieved 12 Feb 2010.
  10. ↑ Amy Farnsworth (2007-08-06). "New coatings cut risk of a dorm fire". The Boston Globe. Archived from the original on August 24, 2007.
  11. ↑ US 2858895,Connell, George A. (inventor),"Methods and compositions for controlling fires",published November 4, 1958.
  12. ↑ "Interagency Standards for Fire and Aviation Operations 2007, Chapter 17" (PDF). National Interagency Fire Center. Archived from the original (PDF) on 2007-09-28. Retrieved 2007-08-31.
  13. ↑ "USDA Forest Service Wildland Fire Chemicals" . Retrieved 2008-11-13.
  14. ↑ US 6676858,Vandersall, Howard L.&Kegeler, Gary H.,"Colorant liquid, method of use, and wildfire retardant liquids containing the same",published January 13, 2004.
  15. ↑ "New fire retardant gel developed that can remain effective for months". 4 October 2019. Retrieved 2020-10-05.
  16. ↑ Qualified Products List
  17. ↑ "Long-Term Fire Retardants – National Technology and Development Program – USDA Forest Service". www.fs.fed.us. Retrieved 2022-01-06.
  18. ↑ "Wildland Fire Chemical Product Information" . Retrieved 2008-11-13.
  19. ↑ "Phos-Chek Wildfire Home Defense FAQs" . Retrieved 2019-09-13.
  20. ↑ "Ember bloc fire gel fact sheet / Technical specs" . Retrieved 2020-10-05.
  21. ↑ "Phos-Chek MSDS" (PDF). Archived from the original (PDF) on March 26, 2023. Retrieved 2008-11-14.
  22. ↑ Bell, Tina; Tolhurst, Kevin; Wouters, Michael (16 May 2005). "Bell, T., Tolhurst, K., and Wouters, M. Effects of the fire retardant Phos-Chek on vegetation in eastern Australian heathlands. International Journal of Wildland Fire. 14(2) 199–211". International Journal of Wildland Fire. 14 (2): 199–211. doi:10.1071/WF04024. S2CID   129368588.
  23. ↑ William Yardley (November 15, 2008). "In Fighting Wildfires, Concerns About Chemicals". The New York Times. Retrieved 2008-11-26.
  24. ↑ "USDA Forest Service Wildland Fire Chemical Systems" . Retrieved 2008-11-13.
  25. ↑ "Wildland Fire Chemical Products Toxicity and Environmental Concerns" (PDF). Retrieved 2008-11-13.
  26. ↑ Dietrich, Joseph P.; Myers, Mark S.; Strickland, Stacy A.; Van Gaest, Ahna; Arkoosh, Mary R. (January 2013). "Toxicity of forest fire retardant chemicals to stream-type chinook salmon undergoing parr-smolt transformation". Environmental Toxicology and Chemistry. 32 (1): 236–247. doi: 10.1002/etc.2052 . ISSN   1552-8618. PMID   23161484. S2CID   5240730.
  27. ↑ Gaikowski, M. P.; Hamilton, S. J.; Buhl, K. J.; McDonald, S. F.; Summers, C. H. (August 1996). "Acute toxicity of firefighting chemical formulations to four life stages of fathead minnow". Ecotoxicology and Environmental Safety. 34 (3): 252–263. doi:10.1006/eesa.1996.0070. ISSN   0147-6513. PMID   8812194.
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