Knowing what foam you have is vital to the safety of the lives and property you are protecting. The type of foam used must be able to protect against the hazard present. When submitting a sample to Dyne, mislabeling the type of foam can lead to false results. To help better assist you in knowing your foam and getting it tested appropriately, below is a summary of the common foam types which are tested at Dyne.
Class B Low Expansion Foam Concentrates
These concentrates are designed to extinguish the two types of Class B flammable liquids. The first type of liquid is a non-polar flammable liquid which does not mix with water, which includes gasoline and your common oils. The second type of flammable liquid is a polar flammable liquid which will mix with water, which includes your common alcohols. Generally, all foams are designed to be used on non-polar solvents but only polar solvent or alcohol resistant concentrates are effective against polar solvents. The type of liquid hazard must be determined before selecting a foam so it provides the right protection. Having an alcohol resistant foam for a nonpolar hazard may not be the best use of funds, for instance. If the hazard is determined to be a Class B liquid, there are a few types of foam available that can be used.
Standard Aqueous Film-Forming Foam (AFFF)
AFFF concentrate is a synthetic foam made with fluorinated surfactants and can produce an air-excluding foam blanket. In addition, AFFF foam solutions provide a vapor sealing film and is designed for use on non-polar flammable liquids only. This foam will appear thin and comes in a variety of colors but most AFFF foams in the field today are amber, yellow, or clear. For all of these foams, keep in mind that if the foam sample is taken from any piping it may have rust or other impurities in it that can change the color.
Alcohol resistant Aqueous Film Forming Foam (AR-AFFF)
AR-AFFF concentrate is essentially AFFF concentrate with the addition of polysaccharide polymer. Polar solvents will destroy standard AFFFs, but the polymer in AR-AFFFs forms a membrane to separate the polar solvent from the foam blanket allowing for use on both non-polar and polar flammable liquids. This foam will appear very thick compared to the standard AFFF and comes in a variety of colors but most AR-AFFF foams in the field today are a viscous amber, viscous yellow, viscous clear/white, or viscous purple. The difference between an AFFF and an AR-AFFF can be determined here at Dyne. Typically the physical properties, especially the viscosity, can be a very good indicator if the foam contains any polymer. Dyne also offers an Alcohol Resistance test which will determine if the foam will truly stand up against a polar solvent.
Protein foams were the first type of mechanical foams used to fight flammable liquid fires. They are made from the hydrolysis of granulized keratin protein. They also contain additives to prevent bacterial decomposition and corrosion. For use on non-polar flammable liquids only (unless labeled as Alcohol Resistant). These foams will appear a very dark brown color and will have a distinct odor. See Figure 1 for a visual example of the differences between an AR-AFFF, AFFF and a protein foam.
Figure 1: From left to right, AR-AFFF, AFFF, and protein foam.
Fluoroprotein foams are protein foams that also contain fluorochemicals for vapor suppression and reduced fuel pick up when applied to non-polar flammable liquids. These foams will appear a very dark brown color and will have a distinct odor.
Film Forming Fluoroprotein (FFFP)
Fluoroprotein foams are protein foams that also contain fluorochemicals for vapor suppression. However, what sets these apart from regular fluorproteins is that the fluorochemical surfactants are generally used at a higher concentration than standard fluoroprotein foam, giving these solutions the ability to form a vapor sealing film on non-polar solvents in a way similar to AFFFs. FFFPs are for use on non-polar flammable liquids. These foams will appear a very dark brown color and will have a distinct odor. The difference between a regular protein and a FFFP can be determined at Dyne. If the lab results show that the foam will form a film, the protein is a FFFP.
Alcohol Resistant FFFP (AR-FFFP)
AR-FFFP foams are essentially FFFP foams with the addition of polysaccharide polymer. Polar solvents will destroy standard FFFPs but the polymer in AR-FFFPs forms a membrane to separate the polar solvent from the foam blanket. These foams will appear a very dark brown color and will have a distinct odor. Again, Dyne can determine if the FFFP is AR based on the results from the optional Alcohol Resistance test.
Class B High Expansion Foam Concentrates
High Expansion foams are designed to have a much higher expansion ratio than low expansion foams, hence the name. These are typically used in large, open areas like an aircraft hangar where the foam will need to fill the area very quickly. They will appear very thin and come in a variety of colors. It may be hard to tell the difference between an AFFF and a high expansion foam by just looking at it. However, Dyne will be able to tell the difference here in the lab. These foams will not form a film but will have very high expansion ratios. On the other hand, AFFF foams put through the high expansion test will not meet the minimum expansion.
Class A Foam Concentrates
By adding Class A foam concentrate to water, the resulting foam spreads over the class A fuel and slowly releases water to cool the fire. The foam concentrate also reduces the surface tension of the water. These foams will appear thin and come in a variety of colors.
Knowing your foam and, if needed, discussing any unusual results with Dyne could save you the cost of foam concentrate replacement. Taking advantage of Dyne’s quick access to chemists can be a great help if you do not know the type of foam you have or need. For more information on firefighting foam testing or specific questions regarding your test results give one of our chemists a call at 800-632-2304.