Fire Streams 487

INTRODUCTIONA fire stream can be defined as a stream of water

or other extinguishing agent after it leaves a firehose and nozzle until it reaches the desired point.The perfect fire stream can no longer be sharplydefined because individual desires and extinguish-ing requirements vary. During the time a stream ofwater or extinguishing agent passes through space,it is influenced by its velocity, by gravity, by wind,and by friction with the air. The condition of thestream when it leaves the nozzle is influenced byoperating pressures, nozzle design, nozzle adjust-ment, and the condition of the nozzle orifice.

Fire streams are intended to reduce high tem-peratures from a fire and provide protection tofirefighters and to exposures through the followingmethods:

• Applying water or foam directly to burningmaterial to reduce its temperature

• Applying water or foam over an open fire toreduce the temperature so firefighters canadvance handlines closer to effect extin-guishment

• Reducing high atmospheric temperature

• Dispersing hot smoke and fire gases from aheated area by using a fire stream

• Creating a water curtain to protectfirefighters and property from heat

• Creating a barrier between a fuel and a fireby covering with a foam blanket

This chapter focuses on several aspects of wa-ter and foam fire streams. The first portion of thechapter includes the elements of what is requiredfor the production of water fire streams, the differ-

Chapter 13

Fire Streams

ent types of streams, and the different types ofnozzles used to produce them. The second part ofthe chapter focuses on the basic principles relatedto fire fighting foams such as how and why foamworks, types of foam concentrates, the generalcharacteristics of foam, how foam is mixed (propor-tioned) with water, application equipment, andfoam application techniques.

EXTINGUISHING PROPERTIES OF WATER[NFPA 1001: 3-3.7(a); 3-3.9(a)]

Water has the ability to extinguish fire in sev-eral ways. The primary way is by cooling, whichremoves the heat from the fire. Another way is bysmothering, which includes water’s ability to ab-sorb large quantities of heat and also to diluteoxygen. When heated to its boiling point, waterabsorbs heat by converting into a gas called watervapor or steam, which cannot be seen (vaporiza-tion). When steam starts to cool, however, its vis-ible form is called condensed steam (Figure 13.1).

Complete vaporization does not happen theinstant water reaches its boiling point becauseadditional heat is required to completely turn thewater into steam. When a water fire stream isbroken into small particles, it absorbs heat andconverts into steam more rapidly than it would ina compact form because more of the water’s surfaceis exposed to the heat. For example, 1 cubic inch(1 638.7 mm3) of ice dropped into a glass of watertakes some time to absorb its capacity of heat.This is because a surface area of only 6 squareinches (3 870 mm2 or 38.7 cm2) of the ice isexposed to the water. However, if that cube of iceis divided into ¹�₈-cubic inch (204.8 mm3) cubesand dropped into the water, a surface area of 48

488 ESSENTIALS

square inches (30 967 mm2 or 309.7 cm2) of ice isexposed to the water. The finely divided particles ofice absorb heat more rapidly. This same principleapplies to water in the liquid state.

Another characteristic of water that is some-times an aid to fire fighting is its expansion capa-

Figure 13.1 Water is found in the solid, liquid, and gaseous states.

bility when converted into steam. This expansionhelps cool the fire area by driving heat and smokefrom the area. This steam, however, can causeserious burn injuries to firefighters and occupants.The amount of expansion varies with the tempera-tures of the fire area. At 212°F (100°C), waterexpands approximately 1,700 times its originalvolume (Figure 13.2).

Figure 13.2 Water expands to 1,700 times its original volume when itconverts to steam.

To illustrate steam expansion, consider anozzle discharging 150 gallons (568 L) of waterfog every minute into an area heated to approxi-mately 500°F (260°C), causing the water fog toconvert into steam. During one minute of opera-tion, 20 cubic feet (0.57 m3) of water is dischargedand vaporized. This 20 cubic feet (0.57 m3) ofwater expands to approximately 48,000 cubicfeet (1 359 m3) of steam. This is enough steam tofill a room approximately 10 feet (3 m) high, 50feet (15 m) wide, and 96 feet (29 m) long (Figure13.3). In hotter atmospheres, steam expands toeven greater volumes.

Steam expansion is not gradual, but rapid. Ifa room is already full of smoke and gases, thesteam that is generated displaces these gaseswhen adequate ventilation openings are pro-vided. As the room cools, the steam condensesand allows the room to refill with cooler air(Figure 13.4). The use of a fog stream in a director combination fire attack requires that adequateventilation be provided ahead of the hoseline(see Chapter 14, Fire Control). Otherwise, thereis a high possibility of steam or even fire rollingback over and around the hose team, and thepotential for injury is great. There are someobservable results of the proper application of a

Fire Streams 489

Figure 13.3 Water’s expansion rate makes it very effective for fire extinguishment.

Figure 13.4 Steam will disperse the products of combustion from an enclosed area with adequate ventilation.

water fire stream into a room: Fire is extin-guished or reduced in size, visibility may bemaintained, and room temperature is reduced.

The steam produced by a fire stream can also bean aid to fire extinguishment by smothering, whichis accomplished when the expansion of steam re-duces oxygen in a confined space.

Several characteristics of water that are ex-tremely valuable for fire extinguishment are asfollows:

• Water is readily available and inexpensive.

• Water has a greater heat-absorbing capac-ity than other common extinguishing agents.

• Water changing into steam requires a rela-tively large amount of heat.

• The greater the surface area of the waterexposed, the more rapidly heat is absorbed.

PRESSURE LOSS/GAIN[NFPA 1001: 3-3.9(a); 3-3.9(b)]

To produce effective fire streams, it is neces-sary to know the effects of factors affecting pres-sure loss and gain. Two important factors thataffect pressure loss and gain in a fire stream arefriction loss and elevation. Pressure changes arepossible due to friction loss in hose and appli-ances. A loss or gain in pressure may result due

490 ESSENTIALS

to elevation and the direction of water flow uphillor downhill.

Friction LossA definition of friction loss as it relates to

water fire streams is as follows: Friction loss isthat part of total pressure that is lost while forc-ing water through pipes, fittings, fire hose, andadapters. The difference in pressure on a hoselinebetween the nozzle and the pumper (excludingpressure lost due to a change in elevation be-tween the two; see Elevation Loss/Gain section)is a good example of friction loss. Friction losscan be measured by inserting in-line gauges atdifferent points in a hoseline (Figure 13.5). Thedifference in the pressures between gauges whenwater is flowing through the hose is the frictionloss for the length of hose between those gaugesfor that rate of flow.

One point to consider in applying pressure towater in a hoseline is that there is a limit to thevelocity or speed at which the water can travel. Ifthe velocity is increased beyond these limits, thefriction becomes so great that the water in thehoseline is agitated by resistance. Certain charac-teristics of hose layouts such as hose size andlength of the lay also affect friction loss.

In order to reduce pressure loss due to friction,consider the following guidelines:

• Check for rough linings in fire hose.

• Replace damaged hose couplings.

Figure 13.5 In-line gauges can be used to show the friction loss between the gauges.

• Eliminate sharp bends in hose when pos-sible.

• Use adapters to make hose connections onlywhen necessary.

• Keep nozzles and valves fully open whenoperating hoselines.

• Use proper size hose gaskets for the hoseselected.

• Use short hoselines as much as possible.

• Use larger hose (for example, increase frombooster hose to 1³�₄-inch [45 mm] hose orfrom 1³�₄-inch [45 mm] hose to 2¹�₂-inch [65mm] hose) or multiple lines when flow mustbe increased.

• Reduce the amount of flow (for example,change nozzle tips or reduce flow set-ting).

Elevation Loss/GainElevation refers to the position of an object

above or below ground level. In a fire fightingoperation, elevation refers to the position of thenozzle in relation to the pumping apparatus,which is at ground level. Elevation pressurerefers to a gain or loss in a hoseline caused by achange in elevation. When a nozzle is above thefire pump, there is a pressure loss (Figure 13.6).When the nozzle is below the pump, there is apressure gain. These losses and gains occur be-cause of gravity.

Fire Streams 491

Figure 13.6 Elevation pressure loss occurs when the nozzle is above thefire pump.

WATER HAMMER[NFPA 1001: 3-3.9(b)]

When the flow of water through fire hose or pipeis suddenly stopped, the resulting surge is referredto as water hammer. Water hammer can often beheard as a distinct sharp clank, very much like ahammer striking a pipe. This sudden stoppingresults in a change in the direction of energy. Thisenergy creates excessive pressures that can cause

Figure 13.7 Water hammer can cause damage to all parts of the water system and to fire equipment.

considerable damage to water mains, plumbing,fire hose, hydrants, and fire pumps. Operate nozzlecontrols, hydrants, valves, and hose clamps slowlyto prevent water hammer (Figure 13.7).

WATER FIRE STREAM PATTERNS ANDNOZZLES(NFPA 1001: 3-3.6(b); 3-3.9(a); 3-3.9(b); 4-3.2(a)]

A water fire stream is identified by its size andtype. The size refers to the volume of water flowingper minute; the type indicates a specific pattern ofwater. Fire streams are classified into one of threesizes: low-volume streams, handline streams, andmaster streams. The rate of discharge of a firestream is measured in gallons per minute (gpm) orliters per minute (L/min).

• Low-volume stream — Discharges lessthan 40 gpm (160 L/min) including thosefed by booster hoselines.

• Handline stream — Supplied by 1¹⁄₂- to 3-inch (38 mm to 77 mm) hose, which flowsfrom 40 to 350 gpm (160 L/min to 1 400 L/

492 ESSENTIALS

min). Nozzles with flows in excess of 350gpm (1 400 L/min) are not recommended forhandlines.

• Master stream — Discharges more than350 gpm (1 400 L/min) and is fed by multiple2¹⁄₂- or 3-inch (65 mm or 77 mm) hoselines orlarge diameter hoselines connected to amaster stream nozzle. Master streams arelarge-volume fire streams.

The volume of water discharged is determinedby the design of the nozzle and the pressure at thenozzle. It is essential for a fire stream to deliver avolume of water sufficient to absorb heat morerapidly than it is generated. Fire stream patternsmust have sufficient volume to penetrate the heatedarea. If a low-volume nozzle producing finely di-vided particles is used where heat is generatedfaster than it is absorbed, extinguishment will notbe accomplished until the fuel is completely con-sumed or its supply is turned off.

The type of fire stream indicates a specificpattern of water needed for a specific job. There arethree major types of fire stream patterns: solid, fog,and broken (Figure 13.8). The stream pattern maybe any one of these in any size classification.

Regardless of the type and size of the firestream, several items are needed to produce aneffective fire stream. All fire streams must have apressuring device, hose, an agent, and a nozzle(Figure 13.9). The following sections more closelyexamine the different types of streams and nozzles.

Solid StreamA solid stream is a fire stream produced from a

fixed orifice, smoothbore nozzle (Figure 13.10). Thesolid stream nozzle is designed to produce a streamas compact as possible with little shower or spray.A solid stream has the ability to reach areas thatother streams might not reach and also minimizesthe chance of steam burns to firefighters. The reachof a solid stream can be affected by gravity, frictionof the air, and wind.

Solid stream nozzles are designed so that theshape of the water in the nozzle is graduallyreduced until it reaches a point a short distancefrom the outlet (Figure 13.11). At this point, thenozzle becomes a cylindrical bore whose length is

Figure 13.8 Fire stream patterns.

Figure 13.9 The four elements that make a fire stream are a pump, hose,a nozzle, and water.

Fire Streams 493

Figure 13.10 A solid stream nozzle.

Figure 13.11 The basic design of a solid stream nozzle.

from one to one and one-half times its diameter.The purpose of this short, truly cylindrical boreis to give the water its round shape before dis-charge. A smooth-finish waterway contributes toboth the shape and reach of the stream. Alter-ation or damage to the nozzle can significantlyalter stream shape and performance.

The velocity of the stream (nozzle pressure)and the size of the discharge opening determine theflow from a solid stream nozzle. When solid streamnozzles are used on handlines, they should beoperated at 50 psi (350 kPa) nozzle pressure. Asolid stream master stream device should be oper-ated at 80 psi (560 kPa).

The extreme limit at which a solid stream ofwater can be classified as a good stream cannot besharply defined and is, to a considerable extent, amatter of judgment. It is difficult to say just exactlywhere the stream ceases to be good. Observationsand tests covering the effective range of fire streamsclassify effective streams as follows:

• A stream that does not lose its continuityuntil it reaches the point where it loses itsforward velocity (breakover) and falls intoshowers of spray that are easily blown away(Figure 13.12)

• A stream that is stiff enough to maintain itsoriginal shape and attain the required heighteven in a light, gentle wind (breeze)

HANDLING SOLID STREAM NOZZLES

When water flows from the nozzle, the reactionis equally strong in the opposite direction, thus aforce pushes back on the person handling thehoseline (nozzle reaction). This reaction is causedby the velocity and quantity of the stream, whichacts against the nozzle and the curves in the hose,making the nozzle difficult to handle. The greater

Figure 13.12 The breakover point is that point at which the stream begins to lose its forward velocity.

494 ESSENTIALS

the nozzle discharge pressure, the greater theresulting nozzle reaction.

ADVANTAGES

• Solid streams maintain better visibility forfirefighter than other types of streams.

• Solid streams have greater reach than othertypes of streams (see Fog Stream section).

• Solid streams operate at reduced nozzlepressures per gallon (liter) than other typesof streams thus reducing the nozzle reac-tion.

• Solid streams have greater penetrationpower than other types of streams.

• Solid streams are less likely to disturb nor-mal thermal layering of heat and gasesduring interior structural attacks than othertypes of streams.

DISADVANTAGES

• Solid streams do not allow for differentstream pattern selections.

• Solid streams cannot be used for foam ap-plication.

• Solid streams provide less heat absorptionper gallon (liter) delivered than other typesof streams.

CAUTION: Do not use solid streams on ener-gized electrical equipment. Use fog patterns withat least 100 psi (700 kPa) nozzle pressure. Do notuse wand applicators because they can be con-ductors.

Fog StreamA fog stream is a fire stream composed of very

fine water droplets. The design of most fog nozzlespermits adjustment of the fog tip to produce differ-ent stream patterns from the nozzle (Figure 13.13).Water droplets, in either a shower or spray, areformed to expose the maximum water surface forheat absorption. The desired performance of fogstream nozzles is judged by the amount of heat thata fog stream absorbs and the rate by which thewater is converted into steam or vapor. Fog nozzlespermit settings of straight stream, narrow-anglefog and wide-angle fog (Figure 13.14). It should beunderstood that a straight stream is a pattern of

the adjustable fog nozzle, whereas a solid stream isdischarged from a smoothbore nozzle.

A wide-angle fog pattern has less forward ve-locity and a shorter reach than the other fog set-tings. A narrow-angle fog pattern has considerable

Figure 13.14 Fog nozzles are most commonly set to a straight stream,a narrow fog, or a wide fog.

Figure 13.13 Adjustable fog nozzles.

Fire Streams 495

forward velocity, and its reach varies in proportionto the pressure applied (Figure 13.15). Fog nozzlesshould be operated at their designed nozzle pres-sure. Of course, there is a maximum reach to anyfog pattern, which is true with any stream. Oncethe nozzle pressure has produced a stream withmaximum reach, further increases in nozzle pres-sure have little effect upon the stream except toincrease the volume.

There are five factors that affect the reach of afog stream:

• Gravity

• Water velocity

• Fire stream pattern selection

• Water droplet friction with air

• Wind

The interaction of these factors on a fog streamresults in a fire stream with less reach than thatof a solid stream. As the list shows, there aremore factors that may negatively affect a fogstream than were given earlier for a solid stream.The more negative factors there are, the less thereach of the stream is likely to be. This shorterreach is why fog streams are seldom useful foroutside, defensive fire fighting operations (Fig-ure 13.16). The fog stream, however, is useful forfighting enclosed fires.

WATER-FLOW ADJUSTMENT

It is often desirable to control the rate of waterflow through a fog nozzle such as when the water

Figure 13.15 A wide-angle fog has less reach and forward velocity. Anarrow-angle fog has greater reach and forward velocity.

Figure 13.16 Fine water particles are easily affected by wind and aircurrents.

supply is limited. Two types of nozzles provide thiscapability: manually adjustable and automatic (con-stant pressure).

Manually adjustable nozzles. Firefighterscan change the rate of discharge from a manuallyadjustable fog nozzle by rotating the selector ring— usually located directly behind the nozzle tip —to a specific gpm (L/min) setting (Figure 13.17).Each setting provides a constant rate of flow aslong as the operator maintains the proper nozzlepressure. The firefighter has the choice of makingflow-rate adjustments either before opening thenozzle or while water is flowing. Depending upon

Figure 13.17 Fog nozzle with selective flow.

496 ESSENTIALS

the size of the nozzle, the firefighter may adjustflow rates from 10 gpm to 250 gpm (40 L/min to1 000 L/min) for handlines and from 300 gpm to2,500 gpm (1 200 L/min to 10 000 L/min) for masterstreams. Most of these nozzles also have a “flush”setting to rinse debris from the nozzle.

CAUTION: Make adjustments to the rate offlow in increments. Major adjustments can causean abrupt change in the reaction force of thehoseline that may throw a firefighter off balance.

Automatic (con-s t a n t - p r e s s u r e )nozzles. Constant-pres-sure nozzles automati-cally vary the rate of flowto maintain an effectivenozzle pressure (Figure13.18). Obviously, a cer-tain minimum nozzlepressure is needed tomaintain a good spraypattern. With this type ofnozzle, the nozzlepersoncan change the rate of flowby opening or closing theshutoff valve (see NozzleControl Valves section).Automatic nozzles allowthe nozzleperson to de-liver large quantities ofwater at constant operat-ing pressures or to reducethe flow to allow for mobility while maintaining anefficient discharge pattern.

CAUTION: Water flow adjustments in manualand automatic fog nozzles require close coordi-nation between the nozzleperson, the companyofficer, and the pump operator.

HANDLING FOG STREAM NOZZLES

Although nozzle designs differ, the water pat-tern that is produced by the nozzle setting mayaffect the ease with which a particular nozzle isoperated. Fire stream nozzles, in general, are noteasy to control. If water travels at angles to thedirect line of discharge, the reaction forces may bemade to more or less counterbalance each otherand reduce the nozzle reaction. This balancing of

Figure 13.18 An automatic nozzle.

forces is the reason why a wide-angle fog patterncan be handled more easily than a straight-streampattern.

ADVANTAGES

• The discharge pattern of fog streams maybe adjusted to suit the situation (see Chap-ter 14, Fire Control).

• Some fog stream nozzles have adjustablesettings to control the amount of waterbeing used.

• Fog streams aid ventilation (see Chapter10, Ventilation).

• Fog streams dissipate heat by exposing themaximum water surface for heat absorp-tion.

DISADVANTAGES

• Fog streams do not have the reach or pen-etrating power of solid streams.

• Fog streams are more susceptible to windcurrents than are solid streams.

• Fog streams may contribute to fire spread,create heat inversion, and cause steam burnsto firefighters when improperly used dur-ing interior attacks (see Chapter 14, FireControl).

Broken StreamA broken stream is a stream of water that has

been broken into coarsely divided drops (Figure13.19). While a solid stream may become a brokenstream past the point of breakover, a true brokenstream takes on that form as it exits the nozzle. Thecoarse drops of a broken stream absorb more heat

Figure 13.19 A broken stream nozzle with applicator.

Fire Streams 497

per gallon (liter) than a solid stream, and a brokenstream has greater reach and penetration than afog stream, so it can be the most effective stream incertain situations. Firefighters use broken streamsmost often on fires in confined spaces, such as thosein belowground areas, attics, and wall spaces.Because a broken stream may have sufficient con-tinuity to conduct electricity, it is not recommendedfor use on Class C fires.

Nozzle Control ValvesNozzle control (shutoff) valves enable the op-

erator to start, stop, or reduce the flow of water,thereby maintaining effective control of thehandline or master stream appliance. These valvesallow nozzles to open slowly so that the operatorcan adjust as the nozzle reaction increases; theyalso allow nozzles to close slowly to prevent waterhammer (force created by the rapid deceleration ofwater). There are three principal types of controlvalves: ball, slide, and rotary control.

BALL VALVE

The design and construction of the ball valve inhandline nozzles provide effective control duringfire fighting with a minimum of effort. The ball,perforated by a smooth waterway, is suspendedfrom both sides of the nozzle body and seals againsta seat (Figure 13.20). The ball can be rotated up to90 degrees by moving the valve handle backward toopen it and forward to close it. With the valve in theclosed position, the waterway is perpendicular tothe nozzle body, effectively blocking the flow ofwater through the nozzle. With the valve in theopen position, the waterway is in line with the axisof the nozzle, allowing water to flow through it.While it will operate in any position between fullyclosed and fully open, operating the nozzle with thevalve in the fully open position gives maximumflow and performance. When a ball valve is usedwith a solid stream nozzle, turbulence caused by apartially open valve may affect the desired streamor pattern.

SLIDE VALVE

The cylindrical slide valve control seats a mov-able cylinder against a shaped cone to turn off theflow of water (Figure 13.21). Flow increases ordecreases as the shutoff handle is moved to changethe position of the sliding cylinder relative to the

Figure 13.20 The operation of a ball valve.

Figure 13.21 The operation of a slide valve.

cone. This stainless steel slide valve controls theflow of water through the nozzle without creatingturbulence. The pressure control then compen-sates for the increase or decrease in flow by movingthe baffle to develop the proper tip size and pres-sure.

498 ESSENTIALS

ROTARY CONTROL

VALVE

The rotary controlvalve is found only onrotary control fognozzles (Figure 13.22).It consists of an exte-rior barrel guided by ascrew that moves it for-ward or backward, ro-tating around an inte-rior barrel. A major dif-ference between rotarycontrol valves andother control valves isthat rotary controlvalves also control thedischarge pattern ofthe stream.

Maintenance of NozzlesFirefighters should inspect nozzles periodically

and after each use to make sure that they are inproper working condition. This inspection includesthe following checks:

• Check the swivel gasket for damage or wear.Replace worn or missing gaskets.

• Look for external damage to the nozzle.

• Look for internal damage and debris. Whennecessary, thoroughly clean nozzles withsoap and water, using a soft bristle brush(Figure 13.23).

• Check for ease of operation by physicallyoperating the nozzle parts. Clean and lubri-cate any moving parts that appear to besticking according to manufacturer’s rec-ommendations.

• Check to make sure that the pistol grip (ifapplicable) is secured to the nozzle.

EXTINGUISHING FIRE WITH FIRE FIGHTINGFOAM[NFPA 1001: 3-3.7(a); 4-3.1; 4-3.1(a); 4-3.1(b)]

In general, fire fighting foam works by forminga blanket of foam on the burning fuel. The foamblanket excludes oxygen and stops the burningprocess. The water in the foam is slowly released as

Figure 13.22 A rotary control nozzle.Courtesy of Elkhart BrassManufacturing Company.

Figure 13.23 Clean nozzles with soap and water when necessary.

the foam breaks down. This action provides acooling effect on the fuel. Fire fighting foam extin-guishes and/or prevents fire in several ways:

• Separating — Creates a barrier betweenthe fuel and the fire

• Cooling — Lowers the temperature of thefuel and adjacent surfaces

• Suppressing (sometimes referred to assmothering) — Prevents the release offlammable vapors and therefore reducesthe possibility of ignition or reignition (Fig-ure 13.24)

Water alone is not always effective as an extin-guishing agent. Under certain circumstances, foamis needed. Fire fighting foam is especially effectiveon the two basic categories of flammable liquids:hydrocarbon fuels and polar solvents. Even firesthat can be fought successfully using plain watermay be more effectively fought if a fire fightingfoam concentrate is added.

Hydrocarbon fuels, such as crude oil, fuel oil,gasoline, benzene, naphtha, jet fuel, and kero-

Fire Streams 499

sene, are petroleum-based and float on water.Fire fighting foam is effective as an extinguish-ing agent and vapor suppressant on Class Bliquids because it can float on the surface of thesefuels.

Polar solvents, such as alcohols, acetone, lac-quer thinner, ketones, esters, and acids, areflammable liquids that have an attraction forwater, much like a positive magnetic pole at-tracts a negative pole. Fire fighting foam, inspecial formulations, is effective on these fuels.

Specialized foams are also used for acid spills,pesticide fires, confined- or enclosed-space fires,and deep-seated Class A fires. In addition toregular fire fighting foams, there are specialfoams designed solely for use on unignited spillsof hazardous liquids. These special foams arenecessary because unignited chemicals have atendency to either change the pH of water orremove the water from fire fighting foams, therebyrendering them ineffective.

Before discussing types of foams and the foam-making process, it is important to understand thefollowing terms:

• Foam concentrate — Raw foam liquid asit rests in its storage container before theintroduction of water and air

• Foam proportioner — Device that intro-duces foam concentrate into the waterstream to make the foam solution

• Foam solution — Mixture of foam concen-trate and water before the introduction ofair

Figure 13.24 Foam cools, smothers, separates, and suppresses vapors.

• Foam (finished foam) — Completed prod-uct after air is introduced into the foamsolution

How Foam Is GeneratedFoams in use today are of the mechanical type

and must be proportioned (mixed with water) andaerated (mixed with air) before they can be used.Foam concentrate, water, air, and mechanical aera-tion are needed to produce quality fire fightingfoam (Figure 13.25). These elements must bepresent and blended in the correct ratios. Remov-ing any element results in either no foam produc-tion or poor-quality foam.

Aeration should produce an adequate amountof foam bubbles to form an effective foam blanket.Proper aeration produces uniform-sized bubbles toprovide a longer lasting blanket. A good foamblanket is required to maintain an effective coverover either Class A or Class B fuels for the periodof time desired.

Figure 13.25 The foam tetrahedron.

Foam ExpansionFoam expansion refers to the increase in vol-

ume of a foam solution when it is aerated. This is akey characteristic to consider when choosing afoam concentrate for a specific application. The

500 ESSENTIALS

method of aerating a foam solution results in vary-ing degrees of expansion that depend on the follow-ing factors:

• Type of foam concentrate used

• Accurate proportioning (mixing) of the foamconcentrate in the solution

• Quality of the foam concentrate

• Method of aspiration

Depending on its purpose, foam can be de-scribed by three types: low-expansion, medium-expansion, and high-expansion. NFPA 11, Stan-dard for Low-Expansion Foam, states that low-expansion foam has an air/solution ratio up to 20parts finished foam for every part of foam solution(20:1 ratio). Medium-expansion foam is most com-monly used at the rate of 20:1 to 200:1 throughhydraulically operated nozzle-style delivery de-vices. In the high-expansion foams, the rate is200:1 to 1000:1.

Foam ConcentratesTo be effective, foam concentrates must match

the fuel to which they are applied. Class A foamsare not designed to extinguish Class B fires. ClassB foams designed solely for hydrocarbon fires willnot extinguish polar solvent fires regardless of theconcentration at which they are used. Many foamsthat are intended for polar solvents may be used onhydrocarbon fires, but this should not be attemptedunless the manufacturer of the particular concen-trate specifically says this can be done. This incom-patibility factor is why it is extremely important toidentify the type of fuel involved before applyingfoam. Table 13.1 highlights each of the commontypes of foam concentrates.

CAUTION: Failure to match the proper foamconcentrate with the burning fuel will result in anunsuccessful extinguishing attempt and couldendanger firefighters.

CLASS A FOAM

Foams specifically designed for use on Class Afuels (ordinary combustibles) are becoming increas-ingly popular for use in both wildland and struc-tural fire fighting. Class A foam is a special formu-lation of hydrocarbon surfactants. These surfac-tants reduce the surface tension of water in the

foam solution. Reducing surface tension providesfor better water penetration, thereby increasing itseffectiveness. When aerated, Class A foam coatsand insulates fuels, protecting them from ignition.

Class A foam may be used with fog nozzles,aspirating foam nozzles, medium- and high-expan-sion devices, and compressed air foam systems(CAFS) (Figure 13.26). Class A foam concentratehas supercleaning characteristics and is mildlycorrosive. It is important to thoroughly flush equip-ment after use. For more information on Class Afoam, refer to IFSTA’s Principles of Foam FireFighting manual.

Figure 13.26 Class A foam may be discharged through a standard fognozzle. Courtesy of Mount Shasta (CA) Fire Protection District.

CLASS B FOAM

Class B foam is used to extinguish fires involv-ing flammable and combustible liquids (Figure13.27 on page 504). It is also used to suppressvapors from unignited spills of these liquids. Thereare several types of Class B foam concentrates;each type has its advantages and disadvantages.Class B foam concentrates are manufactured fromeither a synthetic or protein base. Protein-basedfoams are derived from animal protein. Syntheticfoam is made from a mixture of fluorosurfactants.Some foam is made from a combination of syntheticand protein bases.

Class B foam may be proportioned into the firestream via a fixed system, an apparatus-mountedsystem, or by portable foam proportioning equip-ment. Proportioning equipment is discussed laterin this chapter (see Foam Proportioners section).

Fire S

treams

501TABLE 13.1

Foam Concentrate Characteristics/Application Techniques

Type Characteristics Storage Range Application Rate Application Techniques Primary Uses

Protein Foam — Protein based 35–120°F 0.16 gpm/ft2 — Indirect foam stream so as — Class B fires involving(3% and 6%) — Low expansion (2°C to 49°C) (6.5 L/min/m2) not to mix fuel with foam hydrocarbons

— Good reignition (burnback) NOTE: Fuel should not — To protect flammable and resistance be agitated during application combustible liquids where— Excellent water retention because static spark ignition they are stored, transported,— High heat resistance of volatile hydrocarbons can and processed and stability result from plunging and— Performance can be turbulence from a direct foam affected by freezing and water stream. thawing — Alcohol-resistant must be— Concentrate can be used within seconds of freeze protected with antifreeze proportioning— Not as mobile or fluid — Not compatible with dry on fuel surface as other chemical extinguishing agents low-expansion foams

Fluoroprotein — Protein and synthetic based; 35–120°F 0.16 gpm/ft2 — Direct plunge technique — Hydrocarbon vaporFoam derived from protein foam (2°C to 49°C) (6.5 L/min/m2) — Subsurface injection suppression(3% and 6%) — Fuel shedding — Compatible with simultaneous — Subsurface application to

— Long-term vapor suppression application of dry chemical hydrocarbon fuel storage— Good water retention extinguishing agents tanks— Excellent, long-lasting heat — Must be delivered through — Extinguishing in-depth crude resistance air-aspirating equipment petroleum or other hydro-— Performance not affected carbon fuel fires by freezing and thawing— Maintains low viscosity at low temperatures— Can be freeze protected with antifreeze— May be used with fresh or salt water— Nontoxic and biodegradable after dilution— Good mobility and fluidity on fuel surface— Premixable for short periods of time

continued

502

ES

SE

NT

IALS

Film Forming — Protein based; fortified with 35–120°F Ignited — Must cover entire fuel surface — Suppressing vapors inFluoroprotein additional surfactants that (2°C to 49°C) Hydrocarbon Fuel: — May be applied with dry unignited spills of hazard-Foam (FFFP) reduce the burnback 0.10 gpm/ft2 chemical agents ous liquids (3% and 6%) characteristics of other (4.1 L/min/m2) — May be applied with — Extinguishing fires in

protein-based foams spray nozzles hydrocarbon fuels— Fuel shedding Polar Solvent — Subsurface injection— Develops a fast-healing, Fuel: — Can be plunged into fuel continuous-floating film on 0.24 gpm/ft2 during application hydrocarbon fuel surfaces (9.8 L/min/m2)— Excellent, long-lasting heat resistance— Good low temperature viscosity— Fast fire knockdown— Affected by freezing and thawing— Can be used with fresh or salt water— Can be stored premixed— Can be freeze protected with antifreeze— Alcohol-resistant FFFP can be used on polar solvents at 6% solution and on hydrocarbon fuels at 3% solution— Nontoxic and biodegradable after dilution

Aqueous Film — Synthetic based 25–120°F Ignited — May be applied directly — Controlling andForming Foam — Good penetrating capabilities (-4°F to 49°C) Hydrocarbon onto fuel surface extinguishing Class B fires(AFFF) (1%, — Spreads vapor-sealing film Fuel: — May be applied indirectly by — Handling land or sea crash 3%, and 6%) over and floats on hydrocarbon 0.10 gpm/ft2 bouncing it off a wall and rescues involving spills

fuels (4.1 L/min/m2) allowing it to float onto fuel — Extinguishing most— Can be used through surface transportation-related fires nonaerating nozzles Polar Solvent — Subsurface injection — Wetting and penetrating— Performance may be adversely Fuel: — May be applied with dry Class A fuels affected by freezing and storing 0.24 gpm/ft2 chemical agents — Securing unignited— Has good low-temperature (9.8 L/min/m2) hydrocarbon spills viscosity— Can be freeze protected with antifreeze— Can be used with fresh or salt water— Can be premixed

Type Characteristics Storage Range Application Rate Application Techniques Primary Uses

Table 13.1 continued

continued

Fire S

treams

503 Type Characteristics Storage Range Application Rate Application Techniques Primary Uses

Alcohol- — AFFF concentrate to which 25–120°F Ignited — Apply gently directly onto Fires or spills of bothResistant AFFF polymer has been added (-4°C to 49°C) Hydrocarbon fuel surface hydrocarbon and polar solvent(3% and 6%) — Multipurpose: Can be used Fuel: — May be applied indirectly by fuels

on both polar solvents and May become 0.10 gpm/ft2 bouncing it off a wall and hydrocarbon fuels (used on viscous at (4.1 L/min/m2) allowing it to float onto fuel polar solvents at 6% solution temperatures surface and on hydrocarbon fuels under 50°F Polar Solvent — Subsurface injection at 3% solution) (10°C) Fuel:— Forms a membrane on polar 0.24 gpm/ft2

solvent fuels that prevents (9.8 L/min/m2) destruction of the foam blanket— Forms same aqueous film on hydrocarbon fuels as AFFF— Fast flame knockdown— Good burnback resistance on both fuels— Not easily premixed

High-Expansion — Synthetic detergent based 27–110°F Sufficient to — Gentle application so as — Extinguishing Class A andFoam — Special-purpose, low (-3°C to 43°C) quickly cover not to mix foam with fuel some Class B fires

water content the fuel or — Must cover entire fuel surface — Flooding confined spaces— High air-to-solution ratios: fill the space — Usually fills entire space — Volumetrically displacing 200:1 to 1,000:1 in confined space incidents vapor, heat, and smoke— Performance not affected by — Reducing vaporization from freezing and thawing liquefied natural gas (LNG)— Poor heat resistance spills— Prolonged contact with — Extinguishing pesticide fires galvanized or raw steel may — Suppressing fuming acid attack these surfaces vapors

— Suppressing vapors in coal mines and other subterra- nean spaces; in concealed spaces in basements— As extinguishing agent in fixed extinguishing systems for industrial uses— Not recommended for outdoor use

Table 13.1 continued

continued

504 ESSENTIALS

Figure 13.27 Foam is needed to combat large-scale Class Bfires. Courtesy of Harvey Eisner.

Foams (such as aqueous film forming foam[AFFF] and film forming fluoroproteinfoam [FFFP]) may be applied either withstandard fog nozzles or with air-aspirat-ing foam nozzles (all types) (see FoamDelivery Devices section). The rate of ap-plication (minimum amount of foam solu-tion that must be applied) for Class Bfoam varies depending on any one of sev-eral variables:

• Type of foam concentrate used

• Whether or not the fuel is on fire(Figure 13.28)

• Type of fuel (hydrocarbon/polarsolvent) involved

• Whether the fuel is spilled or in atank (NOTE: If the fuel is in a tank,the type of tank will have a bear-ing on the application rate.)

• Whether the foam is applied viaeither a fixed system or portableequipment

Class A

Foam

— S

ynthetic 25–120°F

The sam

e as—

Can be propelled w

ith—

Extinguishing C

lass A—

Wetting agent that reduces

(-4°C to 49°C

)the m

inimum

compressed air system

s com

bustibles only surface tension of w

ater andcritical flow

rate—

Can be applied w

ith all allow

s it to soak intoC

oncentratefor plain w

ater conventional fire

combustible m

aterialssubject

on similar

department nozzles

— R

apid extinguishment w

ithto freezing

Class A

Fuels;

less water use than other

but can beflow

rates should foam

sthaw

ed andnot be reduced

— C

an be used with regular

used ifw

hen using w

ater stream equipm

entfreezing occurs

Class A

foam—

Can be prem

ixed with w

ater in the booster tank—

Mildly corrosive

— R

equires lower percentage

of concentration (0.2 to 1.0) than other foam

s (1%

, 3%, or 6%

concentrate)—

Outstanding insulating

qualities—

Good penetrating capabilities

Typ

e C

haracteristics

Sto

rage R

ang

e Ap

plicatio

n R

ate A

pp

lication

Tech

niq

ues

Prim

ary Uses

Table 13.1 con

tinu

ed

Fire Streams 505

Figure 13.28 Whether or not the fuel is on fire affects the neededapplication rate.

Unignited spills do not require the same appli-cation rates as ignited spills because radiant heat,open flame, and thermal drafts do not attack thefinished foam as they would under fire conditions.In case the spill does ignite, however, firefightersshould be prepared to flow at least the minimumapplication rate for a specified amount of timebased on fire conditions.

All foam concentrate supplies should be on thefireground at the point of proportioning beforeapplication is started. Once application has started,it should continue uninterrupted until extinguish-ment is complete. Stopping and restarting mayallow the fire and fuel to consume whatever foamblanket has been established.

Because polar solvent fuels have differingaffinities for water, it is important to know applica-tion rates for each type of solvent. These rates alsovary with the type and manufacturer of the foamconcentrate selected. Foam concentrate manufac-turers provide information on the proper applica-

tion rates as listed by UL (Figure 13.29). For morecomplete information on application rates, consultNFPA 11, the foam manufacturers’ recommenda-tions, and IFSTA’s Principles of Foam FireFighting manual.

SPECIFIC APPLICATION FOAMS

Numerous types of foams are selected for specificapplications according to their properties and per-formance. Some are thick and viscous and formtough, heat-resistant blankets over burning liquidsurfaces; others are thinner and spread more rap-idly. Some foams produce a vapor-sealing film ofsurface-active water solution on a liquid surface.Others, such as medium- and high-expansion foams,are used in large volumes to flood surfaces and fillcavities.

Foam ProportioningThe term proportioning is used to describe the

mixing of water with foam concentrate to form afoam solution (Figure 13.30). Most foam concen-trates are intended to be mixed with either fresh orsalt water. For maximum effectiveness, foam con-centrates must be proportioned at the specific per-centage for which they are designed. This percent-age rate for the intended fuel is clearly marked onthe outside of every foam container (Figure 13.31).Failure to follow this procedure, such as trying touse 6% foam at a 3% concentration, will result inpoor-quality foam that may not perform as desired.

Most fire fighting foam concentrates are in-tended to be mixed with 94 to 99.9 percent water.For example, when using 3% foam concentrate, 97parts water mixed with 3 parts foam concentrateequals 100 parts foam solution (Figure 13.32). For6% foam concentrate, 94 parts water mixed with 6parts foam concentrate equals 100 percent foamsolution.

Class A foams are an exception to this percent-age rule. The proportioning percentage for Class Afoams can be adjusted (within limits recommendedby the manufacturer) to achieve specific objectives.To produce a dry (thick) foam suitable for exposureprotection and fire breaks, the foam concentratecan be adjusted to a higher percentage. To producea wet (thin) foam that rapidly sinks into a fuel’ssurface, the foam concentrate can be adjusted to alower percentage.

506 ESSENTIALS

DESCRIPTION

ANSULITE ARC 3%/6% AlcoholResistant Concentrate is formulated fromspecial flourochemical and hydrocarbonsurfactants, a high molecular weightpolymer, and solvents. It is transportedand stored as a concentrate to provideease of use and considerable savings inweight and volume.

It is intended for use as a 3% or 6%proportioned solution (depending on thetype of fuel) in fresh, salt or hard water.(Water hardness should not exceed 500ppm expressed as calcium and magne-sium.) It may also be used and stored asa premixed solution in fresh or potablewater for use with the Ansul Model AR-33-D wheeled fire extinguisher.

There are three fire extinguishingmechanisms in effect when usingANSULITE ARC concentrate on either aconventional Class B hydrocarbon fuelsuch as gasoline, diesel fuel, etc., or aClass B polar solvent (water misciblefuel) such as methyl alcohol, acetone,etc. First, an aqueous film is formed inthe case of a conventional hydrocarbonfuel, or a polymeric membrane in thecase of a polar solvent fuel. This film ormembrane forms a barrier to help preventthe release of fuel vapor. Second,regardless of the fuel type, a foamblanket is formed which excludes oxygenand from which drains the liquids thatform the film or polymeric membrane.Third, the water content from the foamproduces a cooling effect.

ANSUL®

Physicochemical Properties at 77°F(25°C)

Appearance Light Amber Gel-Like Liquid

Density 1.000 + 0.25 gm/ml

pH 7.0 - 8.5

Refractive Index 1.3600 + .0018

Viscosity 2500 + 300 cps*

Chloride Content Less than 75 ppm

*Brookfield Viscometer Spindle #4, Speed 30

ANSULITE ARC Alcohol Resistant Concen-trate is a non-Newtonian fluid that is bothpseudoplastic and thixtropic. Because ofthese properties, dynamic viscosity willdecrease as shear increases.

APPLICATION

ANSULITE ARC 3%/6% AFFF is uniqueamong the ANSULITE AFFF agents in thatit can be used on either Conventional ClassB fuels or the polar solvent type Class Bfuels. Its excellent wetting characteristicsmake it useful in combating Class A Firesas well. Because of the low energy to makefoam, it can be used with both aspiratingand non-aspirating discharge devices.

To provide even greater fire protectioncapability, it can be used with dry chemicalextinguishing agents without regard to theorder of application to provide even greaterfire protection capability. Due to the velocityof the dry chemical discharge, care mustbe taken not to submerge the polymericmembrane below the fuel surface.

ANSULITE®ALCOHOL RESISTANTCONCENTRATE(ARC) 3% AND 6%

EXTINGUISHING

APPLICATION RATESApplication Rates using U.L. 162 Standard 50 ft.2 Fire Test on representative hydrocarbonand polar solvent fuels are listed below.

AlcoholMethanol (MeOH) 6% .10 (4.1) .17 (6.9)Ethanol (EtOH) 6% .10 (4.1) .17 (6.9)Isopropanol (IPA) 6% .10 (4.1) .17 (6.9)

KetoneAcetone 6% .10 (4.1) .17 (6.9)Methyl Ethyl Ketone (MEK) 6% .10 (4.1) .17 (6.9)

Carboxylic AcidAcetic Acid 6% .10 (4.1) .17 (6.9)Glacial

EtherDiethyl Ether 6% .10 (4.1) .17 (6.9)

AldehydePropionaldehyde 6% .08 (3.3) .13 (5.3)

EsterEthyl Acetate 6% .06 (2.4) .10 (4.1)Butyl Acetate 6% .06 (2.4) .10 (4.1)

UL Type II Application (3) - HydrocarbonsHeptane 3% .04 (1.6) .10 (4.1)Toluene 3% .04 (1.6) .10 (4.1)Gasoline 3% .04 (1.6) .10 (4.1)10% Gasohol (EtOH) 3% .04 (1.6) .10 (4.1)

(1) Type III DISCHARGE OUTLET - A device that delivers foam onto the burning liquid and partiallysubmerges the foam or produces restricted agitation of the surface as described in U.L. 162.(2) U.L. builds in a ⁵�₃ safety factor from its test rate to find its recommended rate of application.(3) TYPE III DISCHARGE OUTLET - A device that delivers the foam directly onto the burning liquid asdescribed in U.L. 162.

U.L. Test U.L.(2) RecommendedApplication Rate Application Rate

Fuel Group Concentration gpm/ft2 Lpm/m2 gpm/ft2 Lpm/m2

Figure 13.29 A sample manufacturer’s foam application rate sheet. Courtesy of Ansul Fire Protection.

UL Type II Application (1) - Polar Solvents

Fire Streams 507

Figure 13.30 Foam solution is comprised of foam concentrate andwater.

Figure 13.31 All foam concentrate containers have the properproportioning percentage clearly marked on the outside of the container.

Figure 13.32 Foam generated using a 3% foam concentrate is 3 partsfoam concentrate to 97 parts water.

Class B foams are mixed in proportions from1% to 6%. Some multipurpose Class B foams de-signed for use on both hydrocarbon and polarsolvent fuels can be used at different concentra-tions, depending on which of the two fuels is burn-ing. These concentrates are normally used at a 3%rate for hydrocarbons and 6% for polar solvents.Newer multipurpose foams may be used at 3%concentrations regardless of the type of fuel. Me-dium-expansion Class B foams are typically usedat either 1¹�₂%, 2%, or 3% concentrations. Followthe manufacturer’s recommendations for propor-tioning.

A variety of equipment is used to proportionfoam. Some types are designed for mobile appa-ratus and others are designed for fixed fire pro-tection systems. The selection of a proportionerdepends on the foam solution flow requirements,available water pressure, cost, intended use(truck, fixed, or portable), and the agent to beused. Proportioners and delivery devices (foamnozzle, foam maker, etc.) are engineered to worktogether. Using a foam proportioner that is notcompatible with the delivery device (even if thetwo are made by the same manufacturer) canresult in unsatisfactory foam or no foam at all(see Foam Proportioners and Foam DeliveryDevices/Generating Systems section).

There are four basic methods by which foammay be proportioned:

• Induction

• Injection

• Batch-mixing

• Premixing

508 ESSENTIALS

INDUCTION

The induction (eduction) method of proportion-ing foam uses the pressure energy in the stream ofwater to induct (draft) foam concentrate into thefire stream. This is achieved by passing the streamof water through an eductor, a device that has arestricted diameter (Figure 13.33). Within the re-stricted area is a separate orifice that is attachedvia a hose to the foam concentrate container. Thepressure differential created by the water goingthrough the restricted area and over the orificecreates a suction that draws the foam concentrateinto the fire stream. In-line eductors and foamnozzle eductors are examples of foam proportionersthat work by this method.

Figure 13.33 The operating principles of an in-line eductor.

INJECTION

The injection method of proportioning foamuses an external pump or head pressure to forcefoam concentrate into the fire stream at the correctratio in comparison to the flow. These systems arecommonly employed in apparatus-mounted or fixedfire protection system applications.

BATCH-MIXING

Batch-mixing is the most simple method ofmixing foam concentrate and water. It is com-

monly used to mix foam within a fire apparatuswater tank or a portable water tank (Figure 13.34).It also allows for accurate proportioning of foam.Batch-mixing is commonly practiced with Class Afoams but should only be used as a last resort withClass B foams. Batch-mixing may not be effectiveon large incidents because when the tank becomesempty, the foam attack lines must be shut downuntil the tank is completely filled with water andmore foam concentrate is added. Another draw-back of batch-mixing is that Class B concentratesand tank water must be circulated for a period oftime to ensure thorough mixing before the solutionis discharged. The time required for mixing de-pends on the viscosity and solubility of the foamconcentrate.

Figure 13.34 Batch-mixing can be accomplished by pouring foamconcentrate into the apparatus water tank.

PREMIXING

Premixing is one of the more commonly usedmethods of proportioning. With this method,premeasured portions of water and foam concen-trate are mixed in a container. Typically, the premix

Fire Streams 509

method is used with portable extinguishers,wheeled extinguishers, skid-mounted twin-agentunits, and vehicle-mounted tank systems (Figures13.35 a–c).

In most cases, premixed solutions are dis-charged from a pressure-rated tank using either acompressed inert gas or air. An alternative methodof discharge uses a pump and a nonpressure-ratedatmospheric storage tank. The pump dischargesthe foam solution through piping or hose to thedelivery devices. Premix systems are limited to aone-time application. When used, the tank must becompletely emptied and then refilled before it canbe used again.

Figure 13.35c Twin-agent units may be mounted on hand-pulled cartsor in the back of a truck. Courtesy of Conoco Oil Co.

Figure 13.35a A modernAFFF portable fireextinguisher.

Figure 13.35b A wheeled AFFF fireextinguisher. Courtesy of Conoco Oil Co.

FOAM PROPORTIONERS AND FOAMDELIVERY DEVICES/GENERATING SYSTEMS[NFPA 1001: 4-3.1; 4-3.1(a); 4-3.1(b)]

In addition to a pump to supply water and firehose to transport it, there are two basic pieces ofequipment needed to produce a foam fire stream: afoam proportioner and a foam delivery device (nozzleor generating system). It is important that theproportioner and delivery device/system are com-patible in order to produce usable foam (Figure13.36). Foam proportioning simply introduces theappropriate amount of foam concentrate into thewater to form a foam solution. A foam generatingsystem/nozzle adds the air into foam solutions toproduce finished fire fighting foam. The followingsections detail the various types of foam propor-tioning devices commonly found in portable andapparatus-mounted applications and various foamdelivery devices (nozzles/generating systems).

Figure 13.36 It is important that the proportioner and delivery devicematch each other to produce usable foam.

Foam ProportionersFoam proportioners may be portable or appara-

tus-mounted. In general, foam proportioning de-vices operate by one of two basic principles:

• The pressure of the water stream flowingthrough an orifice creates a venturi actionthat inducts (drafts) foam concentrate intothe water stream (see In-line foam eductorssection).

• Pressurized proportioning devices injectfoam concentrate into the water stream at adesired ratio and at a higher pressure thanthat of the water.

510 ESSENTIALS

PORTABLE FOAM PROPORTIONERS

Portable foam proportioners are the simplestand most common foam proportioning devices inuse today. Two types of portable foam proportionersare in-line foam eductors and foam nozzle eductors.

In-line foam eductors. The in-line eductor isthe most common type of foam proportioner used inthe fire service (Figure 13.37). This eductor isdesigned to be either directly attached to the pumppanel discharge outlet or connected at some pointin the hose lay. When using an in-line eductor, it isvery important to follow the manufacturer’s in-structions about inlet pressure and the maximumhose lay between the eductor and the appropriatenozzle.

In-line eductors use the Venturi Principle todraft foam concentrate into the water stream. Aswater at high pressure passes over a reduced open-ing, it creates a low-pressure area near the outletside of the eductor (See Figure 13.33). This low-pressure area creates a suction effect (VenturiPrinciple). The eductor pickup tube is connected tothe eductor at this low-pressure point. A pickuptube submerged in the foam concentrate drawsconcentrate into the water stream, creating a foamwater solution (Figure 13.38). The foam concen-

Figure 13.37 A typical in-line eductor.

Figure 13.38 The pickup tube issubmerged in a foam container.

trate inlet to the eductor should not be more than6 feet (1.8 m) above the liquid surface of the foamconcentrate. If the inlet is too high, the foamconcentration will be very lean, or foam may not beinducted at all (Figure 13.39).

Figure 13.39 The eductor may be no more than 6 feet (1.8 m) above thefoam concentrate liquid level.

Foam nozzle eductors. The foam nozzle educ-tor operates on the same basic principle as the in-line eductor. However, this eductor is built into thenozzle rather than into the hoseline (Figure 13.40).As a result, its use requires the foam concentrate tobe available where the nozzle is operated. If thefoam nozzle is moved, the foam concentrate also ismoved. The logistical problems of relocation aremagnified by the gallons (liters) of concentraterequired. Use of a foam nozzle eductor compro-mises firefighter safety. Firefighters cannot al-ways move quickly, and they may have to leavetheir concentrate supplies behind if they are re-quired to retreat for any reason.

APPARATUS-MOUNTED PROPORTIONERS

Foam proportioning systems are commonlymounted on structural, industrial, wildland, and

Fire Streams 511

Figure 13.40 A typical handline foam nozzle eductor.

aircraft rescue and fire fighting (ARFF) apparatus,as well as fire boats (Figures 13.41 a–c). Threetypes of the various apparatus-mounted foam pro-portioning systems are installed in-line eductors,around-the-pump proportioners, and balanced pres-sure proportioners. For more information on appa-ratus-mounted proportioners, refer to IFSTA’sPrinciples of Foam Fire Fighting manual.

Figure 13.41a Some structural fire apparatus are equipped with foamsystems. Courtesy of Joel Woods.

Figure 13.41b Many industrial fire apparatus are equipped with foamsystems. Courtesy of Ron Jeffers.

Figure 13.41c Virtually all ARFF apparatus are equipped with largefoam systems.

Foam Delivery Devices (Nozzles/GeneratingSystems)

Once the foam concentrate and water havebeen mixed together to form a foam solution, thefoam solution must then be mixed with air (aer-ated) and delivered to the surface of the fuel.Nozzles/generating systems (foam delivery devices)designed to discharge foam are sometimes calledfoam makers. There are many types of devices thatcan be used, including standard water streamnozzles. The following paragraphs highlight someof the more common foam application devices.

NOTE: Foam nozzle eductors are consideredportable foam nozzles, but they have been omittedfrom this section because they were covered earlierin the Portable Foam Proportioners section.

HANDLINE NOZZLES

IFSTA defines a handline nozzle as “any nozzlethat one to three firefighters can safely handle andthat flows less than 350 gpm (1 400 L/min).” Mosthandline foam nozzles flow considerably less thanthat figure. The following sections detail thehandline nozzles commonly used for foam applica-tion.

Solid bore nozzles. The use of solid borenozzles is limited to certain types of Class A appli-cations. In these applications, the solid bore nozzleprovides an effective fire stream that has maxi-mum reach capabilities (Figures 13.42 a and b).

Fog nozzles. Either fixed-flow or automatic fognozzles can be used with foam solutions to producea low-expansion, short-lasting foam (Figure 13.43).

512 ESSENTIALS

Figure 13.42b CAFS fire streams may be discharged through solid borenozzles. Courtesy of Mount Shasta (CA) Fire Protection District.

Figure 13.42aA solid borenozzle that isused for aCAFS stream.Courtesy ofMount Shasta(CA) Fire Pro-tection Dist-rict.

This nozzle breaks the foam solution into tinydroplets and uses the agitation of water dropletsmoving through air to achieve its foaming action.Its best application is when it is used with regularAFFF and Class A foams. These nozzles cannot beused with protein and fluoroprotein foams. Thesenozzles may be used with alcohol-resistant AFFFfoams on hydrocarbon fires but should not be usedon polar solvent fires. This is because insufficientaspiration occurs to handle the polar solvent fires.Some nozzle manufacturers have foam aerationattachments that can be added to the end of the

Figure 13.43 Film forming foams may be discharged through standardfog nozzles.

nozzle to increase aspiration of the foam solution(Figure 13.44). See IFSTA’s Principles of FoamFire Fighting manual for more information.

Air-aspirating foam nozzles. The most ef-fective appliance for the generation of low-expan-sion foam is the air-aspirating foam nozzle. Theair-aspirating foam nozzle inducts air into thefoam solution by a venturi action (Figure 13.45).This nozzle is especially designed to provide theaeration required to make the highest quality foampossible. These nozzles must be used with proteinand fluoroprotein concentrates. They may also beused with Class A foams in wildland applications.These nozzles provide maximum expansion of theagent. The reach of the stream is less than that ofa standard fog nozzle.

Figure 13.44 Some fog nozzle manufacturers have aeration attachmentsfor their nozzles that can be used during foam operations. Courtesy ofKK Productions.

Figure 13.45 A typical air-aspirating foam nozzle.

MEDIUM- AND HIGH-EXPANSION FOAM GENERATING

DEVICES

Medium- and high-expansion foam generatorsproduce a high-air-content, semistable foam. For

Fire Streams 513

medium-expansion foam, the air content rangesfrom 20 parts air to 1 part foam solution (20:1) to200 parts air to 1 part foam solution (200:1). Forhigh-expansion foam, the ratio is 200:1 to 1000:1.There are two basic types of medium- and high-expansion foam generators: the water-aspiratingtype nozzle and the mechanical blower.

Water-aspirating type nozzle. The water-aspirating type nozzle is very similar to the otherfoam-producing nozzles except it is much largerand longer (Figure 13.46). The back of the nozzleis open to allow airflow. The foam solution ispumped through the nozzle in a fine spray thatmixes with air to form a moderate-expansionfoam. The end of the nozzle has a screen or seriesof screens that further breaks up the foam andmixes it with air. These nozzles typically produce

Figure 13.46 A high-expansion foam tube.

Figure 13.47 Mechanical blowers generate massive amounts of high-expansion foam. Courtesy of Walter Kidde, Inc.

a lower-air-volume foam than do mechanicalblower generators.

Mechanical blower generator. A mechani-cal blower generator is similar in appearance to asmoke ejector (Figure 13.47). It operates on thesame principle as the water-aspirating nozzle ex-cept the air is forced through the foam spray by apowered fan instead of being pulled through bywater movement. This device produces a foam witha high air content and is typically associated withtotal-flooding applications. Its use is limited tohigh-expansion foam.

ASSEMBLING A FOAM FIRE STREAM SYSTEM[NFPA 1001: 4-3.1; 4-3.1(a); 4-3.1(b)]

To provide a foam fire stream, a firefighter orapparatus driver/operator must be able to cor-rectly assemble the components of the system andto locate problem areas and make adjustments.Skill Sheet 13-1 describes the steps for placing afoam line in service using an in-line eductorproportioner:

There are a number of reasons for failure togenerate foam or for generating poor-quality foam.The most common reasons for failure are as fol-lows:

• Eductor and nozzle flow ratings do not matchso foam concentrate cannot induct into thefire stream.

• Air leaks at fittings cause a loss of suction.

• Improper cleaning of proportioning equip-ment causes clogged foam passages (Figure13.48).

• Nozzle is not fully open restricting waterflow.

• Hose lay on the discharge side of theeductor is too long creating excess backpressure causing reduced foam pickup atthe eductor.

• Hose is kinked and stops flow.

• Nozzle is too far above the eductor, whichcauses excessive elevation pressure.

• Mixing different types of foam concentratein the same tank results in a mixture tooviscous to pass through the eductor.

514 ESSENTIALS

FOAM APPLICATION TECHNIQUES[NFPA 1001: 4-3.1; 4-3.1(a); 4-3.1(b)]

It is important to use the correct techniqueswhen manually applying foam from handline ormaster stream nozzles. If incorrect techniques areused, such as plunging the foam into a liquid fuel,the effectiveness of the foam is reduced. The tech-niques for applying foam to a liquid fuel fire or spillinclude the roll-on method, bank-down method,and rain-down method.

Roll-On MethodThe roll-on method directs the foam stream on

the ground near the front edge of a burning liquidpool (Figure 13.49). The foam then rolls across thesurface of the fuel. A firefighter continues to applyfoam until it spreads across the entire surface ofthe fuel and the fire is extinguished. It may benecessary to move the stream to different positionsalong the edge of a liquid spill to cover the entirepool. This method is used only on a pool of liquidfuel (either ignited or unignited) on the open ground.

Bank-Down MethodThe bank-down method may be employed when

an elevated object is near or within the area of a

Figure 13.48 The foam eductor is flushed clean by inserting the pickuptube into a container of clear water for a few moments.

burning pool of liquid or an unignited liquid spill.The object may be a wall, tank shell, or similarstructure. The foam stream is directed off theobject, allowing the foam to run down onto thesurface of the fuel (Figure 13.50). As with the roll-on method, it may be necessary to direct the streamoff various points around the fuel area to achievetotal coverage and extinguishment of the fuel. Thismethod is used primarily in dike fires and firesinvolving spills around damaged or overturnedtransport vehicles.

Rain-Down MethodThe rain-down method is used when the other

two methods are not feasible because of eitherthe size of the spill area (either ignited orunignited) or the lack of an object from which tobank the foam. It is also the primary manualapplication technique used on aboveground stor-age tank fires. This method directs the streaminto the air above the fire or spill and allows thefoam to float gently down onto the surface of thefuel (Figure 13.51). On small fires, a firefightersweeps the stream back and forth over the entiresurface of the fuel until the fuel is completelycovered and the fire is extinguished. On largefires, it may be more effective for the firefighterto direct the stream at one location to allow thefoam to take effect there and then work its wayout from that point.

Figure 13.49 Roll-on foam application.

Fire Streams 515

FOAM HAZARDS[NFPA 1001: 4-3.1; 4-3.1(a)]

Foam concentrates, either at full strengths orin diluted forms, pose minimal health risks tofirefighters. In both forms, foam concentrates may

Figure 13.50 Bank-down method.

Figure 13.51 Rain-down foam application.

be mildly irritating to the skin and eyes. Affectedareas should be flushed with water. Some concen-trates and their vapors may be harmful if ingestedor inhaled. Consult the various manufacturers’material safety data sheets (MSDSs) for informa-tion on specific foam concentrates.

Most Class A and Class B foam concentratesare mildly corrosive. Although foam concentrate isused in small percentages and in diluted solutions,follow proper flushing procedures to prevent dam-age to equipment.

When discussing environmental impact, theprimary concern is the impact of the finished foamafter it has been applied to a fire or liquid fuel spill.The biodegradability of a foam is determined by therate at which environmental bacteria cause it todecompose. This decomposition process results inthe consumption of oxygen by the bacteria “eating”the foam. The subsequent reduction in oxygen fromsurrounding water can cause damage in water-ways by killing fish and other water-inhabitingcreatures. The less oxygen required to degrade aparticular foam the better or the more environ-mentally friendly the foam is when it enters a bodyof water.

The environmental impact of foam concentratesvary. Each foam concentrate manufacturer canprovide information on its specific products. In theUnited States, Class A foams should be approvedby the USDA Forest Service for environmentalsuitability. The chemical properties of Class Bfoams and their environmental impact vary de-pending on the type of concentrate and the manu-facturer. Generally, protein-based foams are saferfor the environment. Consult the various manufac-turers’ data sheets for environmental impact infor-mation.

516 ESSENTIALS

Step 1: Select the proper foam concentrate for the burningfuel involved.

Step 2: Place the foam concentrate at the eductor.

Step 3: Open enough buckets of foam concentrate tohandle the task.

Step 4: Check the eductor and nozzle for hydraulic com-patibility (rated for the same flow).

Step 5: Adjust the eductor metering valve to the samepercentage rating as that listed on the foam concentratecontainer.

SKILL SHEET 13-1 PLACING A FOAM LINE IN SERVICE

In-Line Eductor

Fire Streams 517

Step 6: Attach the eductor to a hose capable of efficientlyflowing the rated capacity of the eductor and the nozzle.

NOTE: If the eductor is attached directly to a pumpdischarge outlet, make sure that the ball valve gates arecompletely open. In addition, avoid connections to dis-charge elbows. This is important because any conditionthat causes water turbulence will adversely affect theoperation of the eductor.

Step 7: Attach the attack hoseline and desired nozzle tothe discharge end of the eductor. Avoid kinks in the hose.

NOTE: The length of the hose should not exceed themanufacturer’s recommendations.

Step 8: Place the eductor suction hose into the foamconcentrate.

Step 9: Open nozzle fully.

Step 10: Increase the water-supply pressure to that re-quired for the eductor. Be sure to consult the manufacturer’srecommendations for the specific eductor.

NOTE: Foam should now be flowing.