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. Coford Glossary "Fire Retardant" 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.
Fire retardants are commonly used in fire fighting, where they may be applied aerially or from the ground.
Commonly used fire retardant additives include mixtures of huntite () and hydromagnesite (), aluminium hydroxide (), and magnesium hydroxide (). When heated, aluminium hydroxide dehydrates to form aluminum oxide (alumina, , releasing water vapor in the process. This reaction endothermic 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, giving fire retardant properties to the materials in which they are incorporated.
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.
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.
Any fire retardant approved for use against wildfires on US Federal lands must be included on the United States Forest Service Qualified Products List. Qualified Products List 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. Phos-Chek is a brand of long-term retardant currently approved for wildland fire use.
Researchers at the University of Southern California’s Department of Civil and Environmental Engineering published a report titled “ Metals in Wildfire Suppressants.” The report provides the first-ever chemical analysis of Phos-Chek fire retardant, which the research team studied because it is the most widely used. The USC researchers found that Phos-Chek contains high levels of heavy metals: 14,400 μg/l of cadmium, 72,700 μg/l of chromium, and 119,000 μg/l of vanadium. These numbers exceed California toxic waste limits by 14 times, 14 times, and five times, respectively.
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. 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.
[https://www.fs.usda.gov/rm/fire/wfcs/products/msds/retard/phoschek/SDS_PC_LC95A-R.pdf Alt URL]but even less-toxic compounds carry some risk when organisms are exposed to large amounts.
As of 2008, drops within 300 feet of bodies of water are generally discouraged unless lives or property are directly threatened.
The US Forest Service is the governing agency that conducts research and monitors the effect of fire retardants on wildland systems in the US.
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 Lethality to fish and other .
Another notable health concern is that fire-suppressant foams are especially toxic to fish in standardized soft and hard water, possibly due to surfactants.
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