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Wildland Fire Chemicals


Summary: The following definitions are used in the USDA Forest Service specifications for wildland fire chemical products and/or these standard test procedures.

Biodegradability. A measure of the decomposition of organic matter through the action of microorganisms.

The following three terms are used to describe the extent to which a product is biodegradable.

  • Readily Biodegradable. A product which is > 60-precent biodegraded within 28 days is considered to be readily biodegradable.

  • Biodegradable. A product which is not > 60-percent biodegraded within 28 days but which is > 60-percent biodegraded by 42 days is considered to be biodegradable.

  • Not Biodegradable. A product which is not > 60-percent biodegraded by 42 days is considered to be not biodegradable.

Class A Foam. Foam for use on fires in Class A fuels.

Class A Fuels. Materials such as vegetation, wood, cloth, paper, rubber, and some plastics in which combustion can occur at or below the surface of the material.

Component. Each combination of ingredients, packaged together by the manufacturer for use in preparation of the mixed product by the user.

  • Mixed product shall be prepared by mixing a single component with water; except that in the case of enhanced water mixtures colored products may be prepared either by mixing a single component with water or by mixing an uncolored single component and a single color component with water.

Coupon, Large Stability. A metal sample, having dimensions of approximately 2 in x 12 in x 1/8 in (5 cm x 30 cm x 0.3 cm), made of mild steel or 2024-T3 aluminum for use in outdoor stability testing.

Coupon, Small Stability. A metal sample, having dimensions of approximately, 1 in x 1 in x 1/8 in (2.5 cm x 2.5 cm x 0.3 cm), made of mild steel or 2024-T3 aluminum for use in indoor stability testing.

Coupon, Corrosion. A metal test specimen, having dimensions of approximately 1 in x 4 in x 1/8 in (2.5cm x 10.2 cm x 0.3 cm), made of 2024-T3 aluminum, mild steel, yellow brass, or Az31B magnesium for use in uniform corrosion testing.

Coupon, Non-Metallic. A test specimen made from any of the required test materials, having dimensions of approximately 1/2 in x 3 in x 1/8 in (1.27 cm x 7.62 cm x 0.3 cm).

Density. The weight in grams of 1 milliliter (mL) of product.

Drain Time. The time that it takes for a specified portion of the total solution contained in the foam to revert to liquid and drain out of the bubble structure.

Dry Concentrate. A dry, single component which is mixed with water to prepare the mixed product.

Enhanced Water Mixture. A wet or dry water enhancer concentrate, mixed with water at a qualified mix ratio.

  • The product is not effective once the water it originally contained has evaporated.

Expansion (or Expansion Ratio). The ratio of the volume of the foam in its aerated state to the original volume of the non-aerated foam solution.

Exposure Cycle. Each exposure cycle shall consist of 1 day (8 to 10 hours) and the following night or weekend.

Fire Point. The lowest temperature at which a liquid will ignite and achieve sustained burning when exposed to a test flame.

Flash Point. The minimum temperature of a liquid at which it gives off sufficient vapor to form an ignitable mixture with the air above the surface of the liquid under specified environmental conditions.

Foam. An aggregation of bubbles created by forcing or entraining air into a foam solution by means of suitably designed equipment or by cascading it through the air.

  • The product is not effective once the water it originally contained has evaporated.

Foam Concentrate. The foaming and wetting agents, and other ingredients, as received from the supplier that, when mixed with water, becomes foam solution.

Foam Solution. The combination of water and foam concentrate (0.1 percent to 1.0 percent, by volume) which is aerated to produce the foam used for actual fire suppression.

  • The addition of foam concentrate to water produces a solution with reduced surface tension which enhanced the wetting ability of the water.

Forest Service. The term Forest Service as used throughout this document refers to the U.S. Department of Agriculture, Forest Service.

Fugitive Color. A coloring agent which imparts a high degree of visibility to the mixed product when first applied to wildland fuels but will gradually disappear over several months.

Hydration. The action of a combination of concentrate with water required to produce a thickened product.

Ingredient. Each single chemical used by the manufacturer in the formulation of the product.

Intergranular Corrosion. A corrosive attack on metal at the grain boundary.

LC50. The concentration of product in water, usually expressed as milligrams of product in a liter of solution that results in the death of 50 percent of the aquatic test specimens within a specified time frame.

LD50. The dosage of a product, usually expressed as milligrams of the product per kilogram of body weight of the test animal, at which 50 percent of the test animals die within a specified time frame.

Long-Term Retardant. A product containing one or more inorganic salts to reduce the intensity of a fire. It contains water which serves to aid in uniform distribution of the retardant salts over the target fuel.

  • The product continues to be an effective fire retardant after the water it originally contained has completely evaporated.

Miscibility. The ability of concentrate to mix with water under specified conditions.

Mixed Product. The combination of a wet or dry concentrate and water at the qualified mix ratio for use in fire management activities.

Mix Ratio. The proportion of concentrate and water in the mixed product.

The mix ratio can be expressed in several ways:

  • Pounds of dry concentrate added to a gallon of water
  • Gallons of wet concentrate to be added to a gallon of water
  • Volume percentage of concentrate and water – typical for foams and wet concentrate water enhancers

pH. A measure of the acidity or alkalinity of a solution, represented on a numeric scale with 7 representing neutral solutions.

  • Higher numbers represent alkaline solutions.
  • Lower numbers represent acidic solutions.

Reduction Index. A measure of the reduction in fire intensity (flame spread and weight loss) during the combustion retarding effectiveness test.

Retarding Salt. A single salt or combination of salts that impart combustion retarding effectiveness.

Sample Container, large. A 5.5-gallon (20 liter), low-density polyethylene carboy without spigot. Carboy shall be closed with a size 13.5 rubber stopper secured by a polypropylene screw cap.

Sample Container, small. A straight-sided, wide-mouth, glass jar having a capacity of approximately 1 quart (946 mL) with non-metallic, screw cap, 89 mm diameter with vinyl-backed fiber liner.

Standard Chemical. Technical grade diammonium phosphate (DAP) mixed with water to produce a 10.6-percent (weight/weight) solution. This solution is used as a reference for the combustion-retarding effectiveness test.

Steady State Viscosity. The viscosity after hydration is complete and viscosity is stable.

Surface Tension. The elastic-like force at the surface of a liquid which tends to minimize the surface area, causing drops to form.

Temperature. Each temperature included in the specification consists of a Fahrenheit temperature and allowable variation from that temperature and the Celsius equivalents for the temperature and range.

Commonly used temperatures and variations are shown in the first section below and included in the specification requirements and test descriptions by listing a simple Fahrenheit temperature.

Other temperatures are described in detail in the second section. Sufficient information is provided within the individual specification requirements and test descriptions to determine the proper choice of conditions.

Fahrenheit Variation Celsius Variation
15oF +5oF -9.4oC +2.8oC
35oF +2oF 1.7oC +1.1oC
40oF +5oF 4.4oC +2.8oC
70oF +5oF 21.1oC +2.8oC
100oF +5oF 37.8oC +2.8oC
120oF +5oF 48.9oC +2.8oC
5oF +2oF -15oC +1oC
35oF +2oF 2oC +1oC
40oF +2oF 4oC +1oC

Uniform Corrosion. Removal of metal by chemical means over the entire surface.

Viscosity. A measure of the resistance of a liquid to flow, expressed in centipoise (cP).

Water, Artificial Sea. A solution of chemicals in deionized water in the prescribed percentages to approximate natural seawater. All percentages are expressed as weight of chemical to total weight of solution.

Water, Deionized. Water treated by distillation, ion exchange, reverse osmosis, or a combination of these methods to remove most salts in conformance to ASTM D-1193 Type IV reagent water.

Water, Fresh. Tap water with a hardness of 120 to 140 ppm of calcium carbonate. A mixture of 3 volumes of ASTM hard water and 1 volume of ASTM soft water as defined in ASTM E-729 may be substituted for the fresh water.

Water Enhancer Concentrate. A concentrate that is added to water to enhance one or more of the physical characteristics of water such as changing the viscosity or elasticity of the water or improving the ability to cling to smooth or vertical surfaces.

Wet Concentrate. A liquid, single component which is added to water to prepare the mixed product.

Wetting Ability. The ability of a solution to spread and penetrate fuel, char, and ash.


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