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INTERNATIONAL FIRE PROTECTION 33

FOAMS

Overview of Fixed Foam Systems

From foam-enhanced sprinklers to high expansiongenerators, foam is used in fixed systems to dealwith a bewildering variety of fire scenarios. How-

ever, one thing that they all have in common – withvery few exceptions – is that flammable liquids arethe fuel source. And when dealing with flammableliquids, using foam that contains fluorosurfactantsusually provides the highest level of fire suppressioncapability.

The science simplified: foam provides a barrieragainst flammable liquid vapors without aggressivelymixing with the product and enhancing the volatilityof fire from the fuel – water alone doesn’t float onhydrocarbons and only serves to make matters worse.On the other hand, foam, especially when it containsfluorosurfactants, suppresses the burning vapor byforming an aqueous film on top of lighter fuels.

How we proportion the foam concentrate withwater, and to what extent we expand it, is deter-mined by the application. It is perhaps more infor-mative to look at the applications first to helpunderstand what choices there are to be made.

Foam Enhanced SprinklersWater is a fantastic firefighting medium, no ques-tion. However, sometimes it needs a little help whenbeing delivered through sprinkler systems. Where asite has a large inventory of plastic material or wherethe storage medium itself is plastic, as in the case of

tote bins, adding foam into the sprinkler nozzles viaa bladder tank gives enhanced fire control. This isclassed as unaspirated foam. In other words, there isno mechanism built into the system for entraining airinto the foam to give any expansion. Because thefoam is only expanded to what might crudely becalled a “milky effect,” the foam concentrate itselfneeds to be aqueous film forming – AFFF.

Foam Deluge SystemsThe difference between deluge and sprinklers,whether we use foam or not, is simply that in a del-uge system a whole zone will actuate and applywater or foam to the hazard. The detection line isseparate and controls the opening of a deluge valveto supply foam/water to the hazard. A range ofdetection options are available from simple aircharged lines with detector bulbs through to triplespectrum UV/IR flame detection. Because deluge sys-tems use open nozzles we have the option to aspi-rate the foam so that it becomes low expansionrather than unsapirated. This is achieved with theuse of nozzles that entrain air and give an expansionratio of up to 20:1 but typically lower. A relatively

gentle application of aspirated foam is to be pre-ferred where solvents in particular are stored.Process hazards are typically where deluge systemsare to be found. Because these are low-expansionsystems, they usually contain fluorosurfactant foamsuch as AFFF or FFFP.

By Tom Cortina

Fire Fighting FoamCoalition (www.fffc.org)

and

David Owen

Firemain Engineering

(www.firemain.com)

Foams for FixedSystems:Fluorosurfactants Add Effectiveness

The negative publicity surrounding 3M’s phase out of PFOS-based fire fightingfoams in 2002, and the subsequent speculation that telomer-based foams mightalso be regulated, has contributed to a shift in recent years in the types of fixed

foam systems being installed in aircraft hangars, warehouses, and other similarapplications. Now that environmental authorities have decided on a voluntarystewardship approach and telomer-based foams have not been regulated, it mightbe time to re-evaluate what are the best agents for use in fixed foam systems.

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Medium Expansion PourersUsing the same methods of proportioning and foamstorage, we can expand most of the commonly avail-able foams up to 200:1. This provides a substantialfoam blanket but with very limited throw from dis-charge devices. It’s ideal where a gentle application

is preferred and where spillage of flammables is con-tained. This is typically into bunds around tank farmsand process areas where bunding is easily achievedwhilst not hindering the means of escape. Mediumexpansion foam was particularly successful at theBuncefield incident for securing the bunds once themore volatile bund fires had been dealt with bymonitors. Medium-expansion pourers can containeither non-fluorosurfactant detergent foam or fluo-rosurfactant foam such as AFFF or FFFP. Most of thefoam used to secure the bunds during the Bunce-field incident was fluorosurfactant foam.

High Expansion FoamAlong with foam-enhanced sprinklers, this is anotherapplication where class B fires are not the only limita-

tion to its use. Expanding foam to anything up to1000:1 means that we have a very light and relativelydry finished foam. One of the main applications forHi Ex systems at present is the protection of aircrafthangars and warehouses. For aircraft hangars, NFPAallows a choice of options including Hi Ex, roof levellow expansion AFFF deluge, and underwing monitorprotection. In recent years Hi Ex has often been cho-sen in preference in part because of environmentalconcerns about fluorosurfactant foams and alsobecause it produces far less firewater run-off, a sig-nificant issue when considering containment.

Despite these concerns, a recent report for theCanadian Department of National Defence recom-mended the use of overhead, closed head watersprinklers with low level, low expansion AFFF foam

as the fire protection system of choice for aircrafthangars. According to the report, the proposed AFFFsystem scored the highest in both technical and costevaluations, is very effective in asset fire protectionwith the AFFF agent utilized, has the ability toachieve rapid delivery and fire control, and is relative-ly simple to install and maintain as all foam compo-nents are located at low level.

Environmental UpdateTelomer-based foams do not contain or degrade intoPFOS. They are not made with PFOA (perfluorooc-tane sulfonate), but may contain trace levels as acontaminant of the manufacturing process. Ratherthan regulate telomer-based products, environmen-tal authorities such as the United States Environmen-tal Protection Agency (EPA) have decided on avoluntary stewardship approach. Under the EPA’sPFOA global stewardship program, telomer produc-ers have committed to 95% reductions of PFOA,PFOA precursors, and related higher homologuechemicals by year-end 2010 and are working towardthe elimination of these chemicals from both plantemissions and finished products by year-end 2015.

Members of the Fire Fighting Foam Coalition thatmake telomer-based fluorosurfactants and AFFF agentsare in position to meet the goals of the global steward-ship program before the 2015 target date with a familyof all C6-based fluorosurfactants that provide the samefire protection characteristics with reduced environ-mental impacts. Incorporating these new fluorosurfac-

tants will require some reformulation and likely sometype of re-approval of most current AFFF, FFFP, and fluo-roprotein foam products between 2010 and 2015.

A new study published recently by SFT related tofluorochemicals found at fire training facilities in Nor-way has drawn interest within the foam industry. The

SFT study confirms the findings of previous studiesthat the likely ultimate biodegradation products ofthe fluorosurfactants used in currently manufacturedAFFF agents are persistent, but are not considered tobe significant environmental toxins. The low bioaccu-mulation values developed in this study reinforce pre-

vious assertions of the general safety of theseproducts. Because these studies were done at firetraining areas where foams were released uncon-trolled numerous times over many years, the findingsshould not be used to assess the impact of a one-timeuse of a fire-fighting foam to extinguish a fire, whichwould result in significantly smaller contaminant con-centrations. Current accepted practice is to use fluo-rine-free training foams whenever possible as well asto collect and treat foam discharges when fluorine-containing foams are used for training or testing.

ConclusionsThere are a number of different types of fixed foamsystems that use both fluorosurfactant and non-fluoro-surfactant foams. Although there has been a small but

discernable trend in recent years towards the use ofnon-fluorosurfactant foams, this trend has been fueledin part by speculation that telomer-based fluorosurfac-tant foams would be regulated. Now that environ-mental authorities have decided on a voluntarystewardship approach and telomer-based foams havenot been regulated, it might be time to be far less anx-ious about telomer based foams and to continue touse the AFFF agents that have provided such provenfire performance in fixed and mobile fire protection.

Fire Fighting Foam CoalitionThe Fire Fighting Foam Coalition, Inc. (FFFC) is a not-for-profit trade association whose members are manu-facturers, distributors and users of aqueousfilm-forming foam (AFFF) fire fighting agents and their

chemical components. The Coalition represents mem-bers’ interests on all issues related to the environmen-tal acceptability of fire fighting foams. FFFC also helpsto ensure that accurate information about PFOS alter-natives, including telomer-based products, is dissemi-nated to appropriate audiences. The Coalition is aclearinghouse for information, supports the develop-ment of industry positions, and interacts on behalf ofmembers with relevant government organizations.

FFFC has provided extensive information on AFFFto environmental agencies in the United States,Europe, and Canada that includes the following:q Amount of fluorosurfactant actives used in the

manufacture of AFFF in the United Statesq Chemical structure of the fluorosurfactants used

in major fluorotelomer-based AFFF formulationsq Mechanics of film formationq Groundwater monitoring data from US military

fire training areasq US Inventory of PFOS-based and fluorotelomer-

based AFFFq Overview of the different types of foams, the

market channel for their distribution, and theenvironmental fate once they are used

q Aquatic toxicity of fire fighting foamsThe following companies are represented on the

Board of Directors of FFFC: Ansul (Tyco), Chem-guard, DuPont, Dynax, and Kidde (UTC). All of usbelieve strongly in the value of our products andtheir potential for fighting fires quickly and safely.Our products have been proven to provide knock-

down, resist burnback and secure the enflamed areain flammable liquid – or class B – fires. From aircraftfires to major flammable liquid spills, our productshave provided quicker, more effective results withless risk to firefighters, less property damage andreduced environmental impact. IFP

34 INTERNATIONAL FIRE PROTECTION

FOAMS FOR FIXED SYSTEMSFOAMS