12 � INDUSTRIAL FIRE JOURNAL � FIRST QUARTER 2010 www.hemmingfire.com
FOAM: THE FUTURE OF AFFF
into the burning fuel. Instead, it must be directed at a horizontalsurface and allowed to flow onto the burning fuel surface.
The US Environmental Protection Agency (EPA) has instituted aglobal stewardship program where fluorochemical manufacturershave voluntarily agreed to reduce 95% by year-end 2010 (andwork to eliminate by year-end 2015) emissions of PFOA(perfluorooctanoic acid), PFOA precursors, and higher homologuechemicals. As a result, telomer-based fluorochemicals that areused in firefighting foams after 2015 are not expected to containeight (C8) and longer perfluorinated carbon chains, in order tocomply with the EPA program. This will require somereformulation and likely some type of re-approval of many currentfoam products between 2010 and 2015. The manufacture andimport of PFOS-based foams is banned in several countries andregions, including the European Union, Canada, and the UnitedStates. Existing stocks of PFOS-based foams must be removedfrom service by 2011 in the European Union and by 2014 inCanada. It is FFFC’s understanding that PFOS-based foams are stillbeing manufactured in China. One of the reasons for thecontinued production may be the misconception that PFOS-basedAFFF agents are more effective than telomer-based AFFF agents.This is simply not true. AFFF agents are equally effective whetherthey contain PFOS-based fluorosurfactants or telomer-basedfluorosurfactants.
The main market driver for the use of aqueous film-formingfoams (AFFF) in general is that they are the most effective agentscurrently available to fight Class B flammable liquid fires at airportsand in military, industrial, and municipal settings. This fact hasbeen consistently proven in fire tests conducted over the past 30years and in tests being performed today. The fluorosurfactantsare key ingredients that provide the required low surface tensionand positive spreading coefficient that enables the formation ofan aqueous film on top of lighter fuels. It is this film formationcapability that gives fluorosurfactant-containing foams theireffectiveness against flammable liquid fires. AFFF agents providerapid extinguishment, burn-back resistance, and protection againstvapour release. Obviously, if there is a polar solvent hazard, anAR-type foam must be employed. The use of gasoline/ethanolblends such as gasohol (nominal 10% ethanol and 90% gasolineor petrol) and E-85 (nominal 85% ethanol and 15% gasoline orpetrol) has increased the potential for large flammable liquid poolor tank fires occurring with these types of products. Beyond theiruse for polar solvent fires, AR type foams have been used verysuccessfully on large tank fires. Their choice in this situation isbased upon the stable, slower draining foams that can beproduced from these types of concentrates.
Some fluorine-free foams can provide an alternative to AFFF insome applications, but they are not currently able to provide thesame level of fire suppression capability, flexibility, scope of usage,and independent validation. A recent paper from the University ofNewcastle shows that even the best available fluorine-free foamwould need to be replenished three times as often as AFFF toprovide the same level of fire protection. Fluorine-free foams areoften championed as “environmentally-friendly” alternatives toAFFF. Although such foams may not contain fluorine, theirenvironmental profile related to biodegradation, acute toxicity,chemical oxygen demand (COD), and biochemical oxygendemand (BOD) is typically no better than fluorine-containingproducts, and in many cases is not as environmentallyresponsible in use as AFFF.
A recent study of commercially available firefighting foamagents indicates that fluorine-free foams are at least an order ofmagnitude higher in aquatic toxicity than AFFF agents. The tworesulting reports are:
• AFC-3A 3% AFFF, Arctic Foam RF3, Aer-o-Water 3EM, F500,
A s with all foams, the primary consideration is performanceon the particular fuel on which the foam will beemployed. Alcohol Resistant (AR) foams that employ
foam stabilizers in addition to the conventional polymers typicallyhave higher performance levels. One should look for foamconcentrates that have the lowest approved application rate onthe fire. Application rates are typically published as l/min/sq.meter or gals/min/sq foot. In addition to performance on fires,the viscosity of the foam concentrate can come into play from alogistics standpoint. Generally, lower viscosity foam concentratesare easier to handle and proportion than are higher viscosityproducts. And, as ambient temperature decreases, the ability toproportion the foam concentrate accurately may become anissue. The end user should ensure that the foam concentrate theychoose is functional with the proportioning equipment theyintend to use it with and at the minimum temperature at whichthey anticipate using the concentrate. One other key issue thatmust be remembered is that all of the current alcohol resistant(AR) foam concentrates currently on the market must be appliedgently on polar fuels. (This is often referred to as a Type IIapplication.) This means that the foam cannot be directly plunged
A future forAFFF foam?Tom Cortina, spokesperson for the US-based Fire
Fighting Foam Coalition expresses the organisation’s
views on the effectiveness of AFFF for class B fires.
A joint exercisebetween
Hampshire FireFRS (UK) and the
Esso FawleyRefinery using high
volume pumps.
12-23 FoamREVrev.qxd 18/12/09 10:20 Page 12
FOAM: THE FUTURE OF AFFF
www.hemmingfire.com INDUSTRIAL FIRE JOURNAL � FIRST QUARTER 2010 � 15
3M RF3 and platinum 3x3 AR AFFF, AcuteEffects on the Fathead Minnow, PimephalesPromelas
• Toxicity Test Results of Six FirefightingFoams using Fingerling Rainbow Trout.
To receive the full reports, email:[email protected]
Chang Jho from the New York-headquarteredDynax Corporation explains the benefits ofpolysaccharide gum-based technology. Currently, alcohol-resistant firefighting foamagents are generally formulated with ahydrophilic biopolymer, such aspolysaccharides. This technology originallyjointly developed by National Foam and CPKelco Corporation in the US in the early 1970shas since been widely used and become themethod of choice for formulating alcohol-resistant foam agents. The polysaccharide is the key component thatmakes the alcohol-resistant foam what it is. On fires involving water-miscible, polar fuels,the polysaccharide precipitates out of the foamblanket forming a membrane at the foam- fuelinterface. This membrane acts as a barrierprotecting the rest of the foam blanket fromcoming in contact with the fuel layer below it.Without this protective membrane, the foamblanket is readily destroyed by the polar fuel.One of the major problems with thepolysaccharide-based AR-AFFFs has been thatthe polysaccharide gum swells and builds highviscosity. Early versions of AR-AFFF’s, therefore,suffered from very high viscosity which in turnlimited some proportioning methods; that isuntil fluorochemical-based “foam stabilizers”were developed.In the early 1990s, Ciba-Geigy developed awater-soluble polymeric fluorochemical andDynax has further improved the chemistry ofthis new class of additives, and termed them“foam stabilisers” which drastically reduced theneed of polysaccharide gums in AR products.This new technology is based on the fact thatthese fluorochemical foam stabilizers are watersoluble, but inherently repellent to polarsolvents such as acetone and alcohol. Thissolvophobicity and synergistic effect with thepolysaccharide gum is what made possible thedevelopment of highly concentrated AR-AFFFagents such as low viscosity 3x3 in the early1990s. The use of fluorochemical foamstabilisers has led to the steady reduction andelimination of polysaccharide gums in theformulation of even higher concentratedalcohol resistant products such as 1x1 AR-AFFFwithout the problems associated with the useof polysaccharides.
Dynax andalcohol-resistanttechnology
Fawley Refinery isthe largestrefinery in the UK,covering somefive square milesand supplying15% of the UK'soil products.Refining activityon the site datesback to 1921.
12-23 FoamREVrev.qxd 18/12/09 10:21 Page 15
