Fire-retardant gel
Fire-retardant gels are superabsorbent polymer
Superabsorbent polymer
Superabsorbent polymers are polymers that can absorb and retain extremely large amounts of a liquid relative to their own mass....

A slurry is, in general, a thick suspension of solids in a liquid.-Examples of slurries:Examples of slurries include:* Lahars* A mixture of water and cement to form concrete* A mixture of water, gelling agent, and oxidizers used as an explosive...

 with a "consistency almost like petroleum jelly." Used as fire retardant
Fire retardant
A fire retardant is a substance other than water that reduces flammability of fuels or delays their combustion. This typically refers to chemical retardants but may also include substances that work by physical action, such as cooling the fuels; examples of these include fire-fighting foams and...

s, they can be used for structure protection and in direct-attack applications against wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...



The practical use of gels was limited until the 1950s as advances in copolymerization techniques led to reproducible, batchwise preparation of swellable resins with uniform cross-linking. This technology was later used in the development of a "substantially continuous, adherent, particulate coating composition of water-swollen, gelled particles of a crosslinked, water-insoluble, water-swellable polymer."

The water-absorbent polymers in fire-retardant gels are similar to those used in diapers.

Mechanism of retardation

The polymer in gels soak up hundreds of times their weight in water creating millions of tiny drops of water surrounded by and protected by a polymer shell. The result is a "bubblet" or a drop of water surrounded by a polymer shell in contrast to a bubble which is air surrounded by liquid. As the gel and water are sprayed onto an exposed surface, millions of tiny "bubblets" are stacked one on top of another. The stacking of the water "bubblets" form a thermal protective "blanket" over the surface to which it is applied. In order for the heat of the fire to penetrate the protected surface, it must burn off each layer of the gel "bubblets" coating. Each layer holds the heat away from the next layer of bubblets beneath. The polymer shell of each bubblets and their stacking significantly prevent water evaporation.

The stacking of the bubblets is similar to aspirated fire fighting foam or compressed air foam systems
Compressed Air Foam System
A compressed air foam system is a system used in firefighting to deliver fire retardant foam for the purpose of extinguishing a fire or protecting unburned areas from becoming involved in flame.-Description:...

, except that bubblets are water filled, whereas foam bubbles are only filled with air. Due to the high specific heat of water, it requires more energy to raise the temperature of water than air. Therefore, water-filled bubblets will absorb more heat than the air-filled foam bubbles (which are more effective for vapor suppression). When gel is applied to a surface such as an exterior wall, the water-filled bubblets can absorb much of the heat given off by the fire, thereby slowing the fire from reaching the wall.

Gels can provide thermal protection from fire for extended periods even at 3500° Fahrenheit. Depending on the fire conditions, applied fire retardant gels offer fire protection for periods of 6 to 36 hours.

After the retained water is completely evaporated from a gel, fire resistance is lost.


During a fire in the Black Hills National Forest
Black Hills National Forest
Black Hills National Forest is located in southwestern South Dakota and northeastern Wyoming. The forest has an area of over 1.25 million acres and is managed by the Forest Service. Forest headquarters are located in Custer, South Dakota...

, "nearly all homes coated with a slimy gel were saved while dozens of houses nearby burned to the ground."

Certain supplemental fire protection insurance may include the application of fire-retardant gel to homes during wildfire. Claimed to work "best when applied hours before a fire approaches", gel is applied using specially designed trucks by private firms. However, danger may be high and private firms may interfere with fire efforts. In response to such a concern, Sam DiGiovanna, chief of Firebreak response program, a private response team, stated: "If whoever is running the fire thinks it's too dangerous to go into a particular area, we don't go into that area."

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