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THUNDERSTORM FC601AFP 1% or 3% AR-AFFF Freeze-Protected concentrate is designed for use in low temperature environments using a new and proprietary technology.  It provides a usable temperature range of -17°C (0°F) to 49°C (120°F).


THUNDERSTORM FC601AFP 1% or 3% AR-AFFF Freeze-Protected concentrate is designed for use in low temperature environments using a new and proprietary technology.  It provides a usable temperature range of -17°C (0°F) to 49°C (120°F).  The foam concentrate has a reduced viscosity as compared to other 1% or 3% listed polar solvent type AFFF concentrates on the market. This reduced viscosity enhances performance in all types of foam proportioning equipment including in-line eductors, balanced pressure systems, and built-in systems aboard CFR vehicles.

Additionally, the firefighting performance of THUNDERSTORM FC601AFP is unmatched by other AR-AFFF foam concentrates. This includes suppressing fires involving the blended gasoline additive Methyl Tertiary Butyl Ether (MTBE) which is being used as an oxygenate to make gasoline cleaner burning. THUNDERSTORM FC601AFP concentrate offers many distinct advantages for ease of use and represents a continued commitment to quality by improving the fire performance of this type of agent on gasoline products while still maintaining high performance levels on other hydrocarbons and polar fuels.

THUNDERSTORM FC601AFP concentrate is formulated from special fluorochemical and hydrocarbon surfactants, high molecular weight polymers and solvents. It is transported and stored as a concentrate to provide ease of use and considerable savings in weight and volume.   With additional components to offer protection against freezing temperature, it provides a superior firefighting foam year round to locations with freezing temperatures in winter.  It contains no PFOS or PFOA ingredients and is biodegradable. It is intended for use as a 1% solution on hydrocarbon fuels and as a 3% solution on polar fuels in fresh, salt or hard water. It may also be stored and used as a premixed solution in fresh potable water only.

There are three fire extinguishing mechanisms in effect when using THUNDERSTORM FC601AFP solution on either a conventional Class B hydrocarbon fuel such as gasoline, diesel fuel, etc., or a Class B polar solvent (water miscible fuel) such as methyl alcohol, acetone, etc. First, an aqueous film is formed in the case of a conventional hydrocarbon fuel, or a polymeric membrane in the case of a polar solvent fuel.  This film or membrane forms a barrier to help prevent the release of fuel vapor. Second, regardless of the fuel type, a foam blanket is formed which excludes oxygen and from which drains the liquids that form the film or the polymeric membrane. Third, the water content of the foam produces a cooling effect.  THUNDERSTORM AR-AFFF foams are also effective foam agents against Class A fires.

Typical Physiochemical Properties at 25°C (77°F)

  • Appearance = Amber Gelled Liquid
  • Density = 1.07 – 1.10 g/ml
  • pH = 7.0 – 8.0
  • Refractive Index = 1.358 min.
  • Typical Viscosity = 1000 CPS*
  • Spreading Coefficient = 5.0 – 7.0
  •  *Brookfield #4 Spindle at 30 rpm

THUNDERSTORM FC601AFP 1% or 3% AR-AFFF freeze protected concentrate is a non-Newtonian fluid that is both pseudoplastic and thixotropic. Because of these properties, dynamic viscosity will decrease as shear increases.


THUNDERSTORM FC601AFP can be used on either conventional Class B fuel or the polar solvent type Class B fuels. Its excellent wetting characteristics make it useful in combating Class A fires as well. Because of the low energy required to make foam, it can be used with both aspirating and non-aspirating discharge devices.  To provide even greater fire protection capability, it may be used with “PKW™” dry chemical extinguishing agent regardless of the order of application. Hydro-Chem™ Technology is a recommended application for dual agent use on a three dimensional fire.  Due to the velocity of the dry chemical discharge, care must be taken not to submerge the polymeric membrane below the fuel surface when using twin agents on polar fuels.

Fire Performance

The fire performance of THUNDERSTORM FC601AFP meets Underwriters Laboratories Standard 162 (Latest Revision) and passes the Williams Fire & Hazard Control Plunge Test.  The UL testing focuses on fuels such as heptane and isopropyl alcohol while the Williams Fire & Hazard Control test focuses on premium unleaded gasoline. THUNDERSTORM FC601AFP was formulated to provide superior performance on all fire tests, especially important is performance on high octane gasoline.

Foam Properties

When used with fresh, salt or hard water at the correct dilution with most conventional foam making equipment, the expansion will vary depending on the performance characteristics of the equipment. Aspirating discharge devices produce expansion ratios of 5:1 to 10:1 depending primarily on type of aspirating device and flow rate. Non-aspirating devices such as handline water fog/stream nozzles or standard sprinkler heads give expansion ratios of 2:1 to 4:1. Medium expansion discharge devices produce typical expansion ratios between 20:1 to 60:1 depending primarily upon type of device and operating conditions.


THUNDERSTORM FC601AFP can be easily proportioned (at the correct dilution) using most conventional proportioning equipment such as:

  • Hydro-Foam™ Nozzles
  • Balanced pressure and in-line balanced pressure pump proportioning equipment
  • Balanced pressure bladder tank proportioner
  • Around-the-pump and Through-the-pump proportioners
  • Fixed or portable (in-line) venturi proportioners
  • Handline nozzles with fixed induction/ pickup tubes

The minimum and maximum usable temperature for THUNDERSTORM FC601AFP in this equipment is -17°C (0°F) to 49°C (120°F) respectively.

Storage/Shelf Life

When stored in the packaging supplied (polyethylene totes, drums or pails) and within the temperature limits specified, the shelf life of THUNDERSTORM FC601AFP is about 20-25 years.  If, however, the product is frozen at temperatures below the low temperature limit during transport or storage, it must be thawed and inspected for signs of separation.  If separation has occurred, the product must be mechanically mixed until homogeneous.  When the concentrate is to be stored in an atmospheric storage tank, a 0.125 to 0.25 in. (3 – 6 mm) layer of mineral oil (Drakeol 35 or its equivalent) should be added to seal the concentrate and minimize the effects of evaporation


Since THUNDERSTORM FC601AFP is a unique blend of surfactants, high molecular weight polymers, and solvents; it is recommended that it not be mixed with any other foam concentrates.  Consult Williams Fire & Hazard Control with any questions of compatibility.

Materials of Construction Compatibility

Tests have been performed with THUNDERSTORM FC601AFP verifying its compatibility with standard carbon steel “black” pipe and pipe manufactured from various stainless steel or brass compounds. Alternative pipe, plastic fittings, and valves may be used in some cases if acceptable to the customer and/or the authority having jurisdiction.

Galvanized pipe and fittings must not be used in areas where undiluted concentrate will contact them since corrosion will result.

Please first consult Williams Fire & Hazard Control for specific guidelines concerning materials of construction.


As with any fire extinguishing agent, THUNDERSTORM FC601AFP, whether in the concentrate or premixed form, should be inspected periodically. NFPA 11 ‘‘Standard for Low Expansion Foam and Combined Agent Systems’’ recommends that samples of foam concentrates stored in containers other than unopened original manufacturer containers should be submitted to the manufacturer or other qualified laboratory for quality condition testing at least annually.

Contact Williams Fire & Hazard Control for further information on annual inspection.

Approvals and Listings

Underwriters Laboratories successfully tested THUNDERSTORM FC601AFP to the requirements contained in U.L. Standard 162, ‘‘Standard for Air-Foam Equipment and Liquid Concentrates.’’ To receive a U.L. listing, the following tests had to be performed successfully:

  • Foam Quality Tests
  • Class B Hydrocarbon Fuel Fire Tests
  • Class B Polar Solvent Fuel Fire Tests
  • Foam Identification Tests
  • Tests of Shipping Containers

FC601AFP is currently UL Listed.  The UL Listed Application rate for Hydrocarbons is 0.10 gpm/sq. ft. The UL Listed Application rate for Alcohols is 0.18 gpm/sq. ft.

In addition to determining agent characteristics, Underwriters Laboratories lists THUNDERSTORM FC601AFP concentrate for use with specific hardware components that also carry the U.L. listing.

Ordering Information

THUNDERSTORM FC601AFP is available in pails, drums, or totes.

 Part   Number Description Approximate   Shipping Weight Approximate   Shipping  Volume
 10534 THUNDERSTORM foam concentrate, 1%X3% AR-AFFF, freeze-protected, FC601AFPP, 5 gallon (19 L) pail 45 lbs. (20.4 kg) 1.25 ft3. (0.035 m3)
 10535 THUNDERSTORM foam concentrate, 1%X3% AR-AFFF, freeze-protected, FC601AFPD, 55 gallon (208 L) drum 495 lbs. (224.5 kg) 11.8 ft3. (0.335 m3)
 10536 THUNDERSTORM foam concentrate, 1%X3% AR-AFFF, freeze-protected, FC601AFP265T, 265 gallon (1000 L) tote 2,463 lbs. (1,117 kg) 31.5 ft3. (0.892 m3)


Environmental Impact

FC601AFP is biodegradable, low in toxicity and can be treated in sewage treatment plants.


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