Nov 2020

Comparison Testing of the New “Fluorine Free” Firefighting Foams

Water alone is typically not effective in controlling or extinguishing fires involving low flash point  ignitable liquids. As a result, foam/water mixtures, utilizing Class B firefighting foams referred to as  Aqueous Film Forming Foams (AFFF) are often used in both manual and fixed fire protection systems for  this hazard. The foams form a film and/or a blanket of bubbles on the surface of ignitable liquid,  preventing the fuel vapors and oxygen from interacting and creating a flammable mixture. 

Due to environmental concerns, the fire protection foams have changed composition in recent years,  due to increasing concerns regarding the environmental and health effects of some of the legacy  constituents (i.e., fluorosurfactants). New foam formulations known as Fluorine Free Foams (FFFs or  “F3” foams) have been introduced and marketed as environmentally acceptable alternatives for legacy  fluorinated foams (often referred to as “C6” or “C8” AFFF foams). 

Anecdotal reports of unexpected variability in the performance of the F3 foams resulted in the Fire  Protection Research Foundation (FPRF) facilitating a test program to evaluate the fire protection  performance and effectiveness of the F3 foams on fires involving hydrocarbon and alcohol fuels. The  objectives of this study were to compare the firefighting capabilities (i.e., control, extinguishment and  burn-back times) for four F3 foams and one short chain legacy “C6” AFFF formulation (as a baseline) for  a range of test parameters including fuel type, water type and fuel temperature. 

The deliverables from the testing were to provide guidance for foam system application standards (e.g.,  NFPA 11: Standard for Low−, Medium−, and High− Expansion Foam) and to identify any additional  research needed to better understand the capabilities and limitations of F3 foams. 

Per UL 162, F3 foams falls under the broad category of “Synthetic (S)” Foams. UL 162 defines a  “Synthetic” foam as one that has a chemical base other than a fluorinated surfactant or hydrolyzed  protein. Since UL 162 was used as the basis of this testing, the test parameters for “Synthetic” foams  were used throughout this testing. During the current revision cycle of NFPA 11, a new category of  foams was proposed to address these new foam formulations (i.e., SFFF; Synthetic Fluorine Free Foams)  thus, the fluorine free foams included in this assessment will likely fall under the “SFFF” category, if  adopted by NFPA 11

Firefighting foams are broken down into two main types depending on the type of ignitable liquid being  protected; H-AFFF (or H-FFF or H-F3) are for fires involving hydrocarbon fuels and AR-AFFF (or AR-FFF or  AR-F3) are “alcohol resistant” foams for use on fires involving alcohol-based fuels. 

A total of 162 tests were conducted, utilizing four fuel types: heptane, gasoline, E10 gasoline, and  isopropyl alcohol (IPA). 

To very briefly summarize the results, the legacy C6 AR-AFFF demonstrated superior firefighting capabilities through the entire test program under all test conditions. The AR-AFFF performed well  against all test fuels included in this assessment (IPA, heptane, gasoline and E10 gasoline). 

The F3 foams did well against heptane but struggled against the other fuels (IPA, gasoline and E10  gasoline) especially when the foam was discharged with a lower foam quality and/or amount of 

aspiration. From an application rate perspective, the F3 foams typically required between 1.5 to 3 times  the application rates to produce comparable performance as the legacy AFFF. 

When comparing the capabilities of the AR-F3 and H-F3 foams, the H-F3 foams typically demonstrated  better capabilities. In general, the needed extinguishment densities for the AR-F3 foams were higher  than that of the H-F3 foams.  

Due to its properties, legacy AFFF has two separate mechanisms that combine to aid in the  extinguishment of an ignitable liquid fire; a surfactant film that forms on the fuel surface and a foam  blanket which both serve to seal in the flammable vapors that are burning above the fuel surface  resulting in extinguishment. 

The F3 foams have only the foam blanket to seal in the vapors. As a result, the capabilities of F3 foams are highly dependent on the characteristics of the foam blanket, which depends on the associated  discharge devices as well as the foam type itself.  

The test results also show that the legacy fuel (heptane) used to test and approve foams, may not be a  good surrogate for all hydrocarbon-based fuels. Specially, some foams struggled against other fuels (like  gasoline) as compared to heptane. The report recommended that going forward, the F3 foams be tested  and listed for a variety of hydrocarbon fuels (e.g., gasoline, E10, Jet A, etc.), similar to the approach  currently used for polar solvent listings. In addition, the amount of aspiration and foam qualities (i.e.,  expansion and 25% drainage), should be included on the UL listing data sheet(s). Additional research is  currently being conducted by other organizations to identify a range of optimal foam properties (which  may be manufacturer specific). 

Ultimately, end users will need to design and install F3 foams within the listed parameters in order to  ensure a high probability of success during an actual event. This applies to the not only to the discharge  devices but also to the proportioning systems as well (due to the highly viscous nature of some of the F3 concentrates).  

Contact Risk Logic to help determine the best firefighting foam to use at your facility.

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