NFPA and other recognized standards recommend the testing of low expansion concentrate be done annually to ensure that the integrity of the foam is holding up over time.  A failing result on a Dyne Fire Protection Labs test report may lead to an investigation to either replace the foam concentrate or equipment, which can cost money and time. 

It is important to understand the reasons why your firefighting foam concentrate may be failing as various factors can contribute to a sample failing.  Additionally, this knowledge may be helpful when sending samples in for testing.  Common causes of a foam sample failing include incorrect product information, dilution, aging, improper storage conditions, mixing incompatible foam, and improper sampling technique.

Incorrect Product Information: 

Incorrect product information, such as foam type and % concentration, can lead to undesired results.  It is important to know what type of foam you have and what foam type is required for the hazard against which you are protecting.  Different foam types have different requirements and tests.  For example, an AFFF (Aqueous Film Forming Foam) tested as an AR-AFFF (Alcohol-Resistant Aqueous Film Forming Foam) will likely fail for drain time and viscosity; a protein-based foam will likely fail for film formation and spreading coefficient if tested as a FFFP (Film Forming Fluoro Protein).  Make sure to indicate all the required information on the sample return form.


Dilution in a foam tank can be an issue since it causes less foam concentrate to be present in your produced foam. In other words, if your foam is meant to be proportioning at 3%, but it is diluted with water, the foam solution that comes out of the tank will be less than 3%.  Foam mixed at lower concentrations than what is required will not perform as there is simply not enough surfactant present. 

An alternative reason for a failing sample that has been contaminated with water is that there are certain foams on the market that are not designed to be premixed with water for long periods of time and stored. Surfactants in this situation could break down over time.

Foam concentrate that has been contaminated with water will typically be identified by lower density, refractive index, and viscosity (if alcohol-resistant) values on a Dyne test report.  Because of the lower physical properties of water, the diluted foam concentrate will typically be found near the top of the tank.  This may cause a passing bottom sample and a failing top sample.  In the field, a field refractometer can be of use in identifying water issues using a refractive index as a reference.


Aging of foam concentrate will occur naturally over time as the chemical ingredients break down and the solvent in the foam evaporates.  If the foam is showing low performance and is outside the shelf life, the failure might simply be caused by the normal breakdown of the foam.  Aging can be accelerated by improper storage conditions.  If you have any questions or concerns about the shelf life of your foam concentrate, Dyne suggests contacting the manufacturer of your foam.

Improper Storage Conditions:

Acceptable storage temperatures are often indicated by the manufacturer on the product data sheet.  Extreme temperatures outside this recommended range can be damaging to the integrity of the foam concentrate.  High temperatures are a concern because chemical reactions typically happen at high temperatures where the heat will provide the necessary energy for a chemical to react and break down – most manufacturers recommend not storing foam in direct sunlight and typically, foams should not be stored above 120 degrees Fahrenheit.

Mixing Incompatible Foam:

Mixing different types or brands of foam can lead to chemical reactions where the foam’s ingredients will break down and become less effective.  Each manufacturer has their own formulation of chemicals in foam to give them their desired performance.  Since the exact content of the foam is considered a trade secret and is not published, it cannot be determined how exactly two foams will react.  While the reaction shouldn’t be violent, it can be enough to render a surfactant useless.  If incompatible alcohol-resistant foams are mixed, the polymer might drop out of solution which could create issues in a proportioner.  To eliminate the uncertainty of this situation, NFPA 11 does not recommend that two different types of foam be mixed.  If a tank is in need of topping off, the same product should be used. 

Improper Sampling Techniques:

Taking a sample improperly can also lead to failed annual testing results.  For bladder tanks, make sure to identify and sample the concentrate and not the bladder water.  Sending in bladder water indicated as a concentrate could lead to the belief that the sample is diluted as it will certainly fail the performance testing no matter the type of foam. 

Taking a sample directly from a test port or piping without allowing the concentrate to flow through may lead to a sample that is not representative of the tank. This sometimes leads to the presence of rust in the sample, which may hinder the performance properties of the foam.

It is always a good idea to take more than one sample from a tank at different places to ensure the foam is performing throughout.  Only a portion of the tank may fail but this will only be caught if multiple samples are taken at different areas.  For example, small amounts of water may rise to the top of some tanks.  If it is a small amount, only a portion of the top may be diluted which can be removed and topped off.

Try to avoid any mineral oil layers when taking samples as well.  Mineral oil is placed on the top of some foams to help avoid any solvent evaporation.  This mineral oil can lower the foam’s performance if it is mixed in the foam.  Always ensure the sample was taken correctly before making any conclusions on failed results.

Should you need any more information regarding why your foam concentrate sample may be failing, please contact Dyne Fire Protection Labs at (800)632-2304 or

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