Think of air aspirated foam systems as that fancy soap-filled spray attachment you use to wash the fire truck. Water and liquid soap meet at the nozzle, combine and cover the truck in suds. Finding an equivalent for a compressed air foam system is not as easy. The closest is the tube that carries your deposit to the teller at a drive-through bank.
Making air aspirated foam is largely a matter of hydraulics, said Dominic Colletti, foam systems product manager for Hale Pumps. By comparison, compressed air foam merges hydraulics with pneumatic technology to produce a richer, thicker, higher-quality fire fighting foam and extend the reach of the unit's nozzle.
"Firefighters are familiar with water and hydraulics," Colletti said. "Now what we are doing is putting compressed air and foam solution together, giving you a liquid and air pneumatic content in the hoseline. I use the phrase 'hydro-pneumatic' to describe it."
CAFS technology, long accepted as an important tool in wildland fire fighting, is finally gaining ground in military, aviation and structural fire fighting after its faultering introduction in the 1970s and 1980s. Understanding the advantages and drawbacks of CAFS is important in making a fair determination if this technology can be adapted to the special needs of your fire department, brigade or emergency response team.
Aspirated nozzles create finished foam at the working end of the hose. By use of an eductor or direct injection, air is sucked into the nozzle causing the pressurized combination of foam solution and water to exit as foam. With CAFS the process starts much earlier. Foam is produced by combining pressurized air with water and foam concentrate at the unit's pump. When it exits the hose under pressure, the foam has a rich, thick consistency most often compared to shaving cream.
Clarence Grady, foaming systems manager for Pierce Manufacturing, describes CAFS units as using a "high back pressure aerator."
"Conventional systems aerate foam by pushing it through an air aspirated nozzle or just accepting what foaming occurs when you throw it through the air," he said. "A compressed air foam system forces the air that creates the foam into the fire stream either through the piping or the handline."
Not all CAFS units use a compressor, though. Some, such as the Tri-Max, use compressed gas stored in pressurized bottles. Tri-Max coldcaf technology, developed by former Army helicopter pilot David Mahrt, is manufactured by Crash Rescue Equipment Service, Inc., through agreement with Mahrt's California-based company, Kingsway Sales. Initially, the product was designed to protect helicopters during refueling in place of older Halon units.
"You take and inject high pressure air into a solution stream," Mahrt said. "This solution stream is water and chemical mixed. We use pressure vessels that store the pre-mixed solution of foam and water. Then when we pressurize that solution, the air pressure moving through our patented manifold system both pushes the water and then expands it."
The benefits are instantly apparent. Compared to foam aspirated at the nozzle, CAFS foam has an almost microscopic bubble structure that makes it long lasting and able to stick to vertical surfaces such as threatened exposures. Energy from the air compressor greatly extends the discharge reach. Because the hose is mostly filled with air instead of water, it weighs less and is easier to move. Pressure loss due to elevation is drastically reduced. The system is extremely economical as to the amount of water and foam concentrate used.
Then why do aspirated foam systems prevail as the fire service standard? In a CAFS unit it is critical that the pressures between the air and water/foam solution be carefully balanced to preserve the quality of the foam. In the early years of CAFS development this was a difficult process for operators to master. Today, the process has been automated.
Odin Foam, a division of W.S. Darley, is also a CAFS unit manufacturer. Jim Guse, division administrator at Odin, said a CAFS unit can be as complicated or as simple as the job demands. His preference is to reduce the complications where possible.
"It's an easy technology but there is enough complication to the system where if people don't build it quite right then it just doesn't work real well," Guse said. "That can give people a black eye. Over the years that's what happened. Some of the original systems just weren't easy to operate and maintain. Nowadays the evolution have moved to the point they are."
Simple or not, firefighters tend to regard any new technology with skepticism. However, the learning curve in mastering CAFS technology is not as steep as you might think.
Compressed air foam is a 'high energy' system. The stream projected from a mid-sized CAFS unit can easily knock a firefighter down, even at a distance as great as 200 feet. An unwary firefighter fooled by the light hose line can easily find himself flying backwards when he opens the nozzle. What gives the unit its staggering energy is the air compressor.
Firefighters using CAFS to protect exposures often have to back away rather than get closer, said fire protection engineer Larry Davis, formerly of Refinery Terminal Fire Company and Industrial Emergency Services in Corpus Christi, TX. Davis' expertise is in industrial fire protection.
"Lets say we had a hose line using nozzle aspirated foam," he said. "I have a pump that can put out 150 to 200 psi (pounds per square inch) coming off my fire pump. Now with compressed air foam I not only have the energy that the pump has given me but I also have the tremendous energy from the air compressor.
"If I went to foam down a building I'd probably have to be 100 feet away from it with CAFS. If I was close to it I'd splatter foam everywhere."
The Canadian company Snuffer makes units as large as 425 cfm. Most of its CAFS sales are in the 50 - 250 cfm range, said Harry Crawley, Snuffer's director of engineering. But even with its 40-gpm CAFS unit, the smallest Snuffer makes, a distance of 60 to 80 feet is not unreasonable, he said.
"You can throw CAFS foam as far as you can shoot water," Crawley said.
His estimate is conservative. Most CAFS manufacturers, such as Colletti at Hale, maintain that the extra kick from the air compressor gives their unit a reach that exceeds its equivalent in aspirated systems.
"You get as good a reach up to one-third better, depending on how your system is set up," said Colletti. "The compressed air not only generates the bubbles inside the apparatus but it also adds horsepower from the air compressor to propel the foam stream."
According to Guse at Odin, the drawback with aspirated nozzles that is impossible to overcome is that the design robs horsepower from the foam system that shortens its reach.
"To make this nozzle you had to restrict the water and create a venturi, (i.e., a tube with a constrict section at the center that lowers the pressure and increases the velocity of fluid flowing through it)," Guse said. "When you do that you've lost your reach. That's a negative. You've ended up with a real wet foam which is better than plain old water but not as good as CAFS."
Even in areas where water is plentiful, the CAFS unit compressor gives firefighters an edge where it counts most, said Colletti at Hale.
"Say you have a municipal pumper with a 2,000 gpm pump and a hydrant right in front of a burning one-story home," Colletti said. "The firefighters are going to make an interior attack pulling an 13/4-inch line with them. So even though you've got a great water supply behind you and a big pump, you're still limited with the line and the flow rate you can get out of it. If you use that 125 gpm line with compressed air foam you can make it work like it was a 300 gpm line. You're going to be better equipped to stop the fire."
The hose those firefighters will be pulling is lighter because it is filled with compressed air foam, not water. The hose is actually light enough to float on water. John Breedlove, director of product development for Colorado-based Intelagard, cited a recent example he witnessed
"The Colorado Division of Forestry had one of our small CAFS units in the back of a pickup," he said. "They fought a brush fire near where I live. They had 1,500 feet of 1-inch hose laid out slightly up hill and were still throwing a 75-foot stream from the nozzle. If you tried to do the same thing with water you're going to have to have a couple of booster pumps in there just to get the water to the nozzle."
Besides elevation, the friction loss as water moves through that hose also reduces the flow rate, Breedlove said. Flowing bubbles instead of water reduces the friction loss and increases the discharge.
But the air compressor is also the major limiting factor with CAFS units. The largest aspirated nozzles used in industrial fire fighting flow 14,000 gpm. The standard used throughout industrial fire fighting is 2,000 gpm. The equal to that in CAFS would require either a plant air loop or a compressor on its own trailer, said Grady at Pierce.
"If you look around there are some massive air compressors out there that are 1,000 cfm," he said. "But even at that you would be limited to a couple of thousand gallons per minute. We've done a couple of large scale stream tests just to watch it work, about 2,500 gpm and 1,000 cfm of air. It makes an excellent foam and it really punches it out there but there isn't enough known about the large-scale end of things, such as what the critical application rates would be."
The largest practical units built by Pierce were powered by 400 cubic foot air compressors, Grady said. These units produce a 'wet' grade of foam at solution flow rates of between 1,200 gpm and 1,500 gpm.
"The Los Angeles City Fire Department has some foam tenders that have 400 cubic foot compressors on them," Grady said. "We are building a Schwing unit for the city of Phoenix that has an 85-foot boom with a 4,000 gpm nozzle and a 400 cubic foot compressor on it."
A mobile air compressor big enough to operate a CAFS unit has advantages beyond fire fighting, said Guse at Odin.
"You can use that air to run air holders that pump off certain liquids," he said. "You can use foams for the CAFS unit to do washdowns and decontaminations. It really is a multifunction tool. You can isolate water, your foam injection system and your air and use each individually. In an explosive environmental area you can lay out your fire hose and just put air in it. Then, from an air holder -- non explosive type -- you can run equipment off it without the risk of using a gas motor or fan."
Still another use for the compressor is filling inflatable lifting bags used in rescue from collapsed structures, Guse said. The standard among the big names in CAFS is rotary screw compressors. Guse said nothing less than a full blown industrial air compressor should be considered for the rigors that fire equipment undergo. Some prefer not to use a compressor at all. The Tri-Max fire suppression system operates from compressed air tanks. The Tri-Max not only operates in subfreezing conditions, it produces foam that is subfreezing.
"Ours is the only system that works at a -40 degrees C," said Mahrt. "We have a chemical, an AFFF chemical, that works at -40 degrees C. Hundreds of our units are outfitted with that chemical in the northern zones when the temperature outside drops below freezing."
"In our case, we patented the cold foam technology where the air drops well below zero as it comes out of the air bottle. When it comes rushing the Bernoulli principal takes effect. That means that it gives up its BTUs of heat as it is rushing out into the atmosphere or into some other area. Its temperature drops significantly, becoming much, much colder and that coldness is transferred into the foam stream. That coldness has a major effect on fire behavior. When compressed air foam units are used with air compressors, those air compressors will raise the temperature of the air close to 200 degrees, where our compressed air foam program lowers the temperature of air well below freezing. But it doesn't cause the system to freeze up. It's moving too fast for that."
Borrowing from aspirated foam technology, that cold foam is delivered to the target via a Williams Fire & Hazard Control Hydro-Chem TM twin agent nozzle which encapsulates dry chemical through the center of the foam stream.
Leading CAFS manufacturers report that more units are now being purchased by fire departments than used for wildland fire fighting. And while some big cities such as Los Angeles, Houston and Phoenix utilizing CAFS, the place it has gained a true foothold in structural fire fighting is with rural and small town fire departments.
With CAFS units selling for thousands more than conventional aspirated foam systems, why are the small departments taking the plunge. The reason is simple -- water. One example cited by Guse at Odin is fire departments throughout the Black Hills of South Dakota.
"We've got about 20 CAFS units out there," Guse said. "And these departments are not real rich. A lot of them are using CAFS for initial attack, say as a rescue unit responding to a car fire. It used to be you needed 500 gallons of water to put out a good car fire. Now you can do a knockdown with about 25 gallons of water. And with us you don't take up as much room with the tank and other things."
The basic idea behind the use of foam as a fire fighting agent, CAFS or aspirated, is that turning water into bubbles increases its extinguishing properties. Water can be effectively distributed over a greater surface area. Compressed air foam expands water to between five and 15 times its original volume. This means a great deal more can be done with the limited water available to some departments, said Crawley at Snuffer.
"CAFS uses less water by far than any other fire fighting system, whether it is plain water or aspirated foam," Crawley said. "That's really why we have been particularly successful in rural fire departments where a lack of water is very often the cause of losing the structure."
Small fire departments can see the benefit from a CAFS unit immediately, said Colletti at Hale.
"They've got to carry all that water with them," Colletti said. "If they can make that water work three, four, five times better, they are using that water supply more effectively."
That efficiency with water can be just as important in town as in the countryside. Small towns sometimes means small water mains. With greater emphasis placed on the energy provided by the air compressor, water pumps used with CAFS are much smaller than most firefighters are used to operating. Most manufacturers offer centrifugal pumps. CFX is one exception. Looking for a use for its plastic positive displacement pump, CFX entered the CAFS market eight years ago.
"We have one of the lowest application rates," CFX president Eddie Paul said. "Because of positive displacement our pump it mixes better. We've had it down to less than .1 percent of foam concentrate. Most the units mix CAFS at the pump. We mix the compressed air foam at the intake so it goes through the pump and gets agitated more. It whips up a better foam."
At CFX, Paul said he keeps hearing the same statement over and over from prospective customers when comparing CAFS to aspirated foam systems -- "Water is free and its everywhere."
But the issue with water is not always a matter of quantity. Sometimes it is a matter of time.
"If you've got 500 gallons of water and you're pumping 100 gallons per minute that's five minutes," said Paul. "If you use CAFS you use a gallon a minute and you've got 500 minutes."
Neel Associates makes both aspirated and compressed air foam systems. Although CAFS do use less water, Neel's general manager Gene Lednicky said he will still put his aspirated foam equipment against a CAFS unit with regard to fire fighting effectiveness. Cost and the easy availability of water in some communities dampens interest in CAFS, he said.
"Most of these departments now have water where they used to need tankers," Lednicky said. "The water is actually what is putting out the fire. If you are putting too much foam or too thick a layer, particularly as a barrier maybe for a grass fire, heck, it's sitting up there on top of the grass. A fire can actually burn under that thing. A little wetter foam is what you're going to need. I don't know how much water you're saving when you get to that point."
Beyond quantity and time, the water issue extends to manpower too. Guse at Odin said CAFS' increased efficiency and effectiveness means a short staffed fire department can do more with the firefighters available on short notice.
"You might not have any backup personnel to allow you to make an interior attack with a backup line as per NFPA standards," he said. "So you might spray it through the window and down the hall, through the doorway without ever entering the structure and still knock it down with CAFS before the neighboring department 30 miles away finds three guys to respond in mutual aid."
CAFS is not a replacement for a full-size pumper in all situations, Guse said. But it is effective in enough situations that small communities are choosing it as an alternative to a major fire truck purchase.
"If you can become 8-to-10 times more effective with a small one, you can see the ramifications on these small towns that don't have big budgets," Guse said. "They spend their money on a Ford 550 with a nice little CAFS unit and do an exterior attack instead."
Other water-related benefits stem from using CAFS technology, said Crawley at Snuffer. Environmental impact from fire water runoff is an increasing concern.
"We can very often put out a structural fire like a house fire with zero runoff," Crawley said. "You don't contaminate the groundwater."
Still another issue to consider is firefighter safety. Because water is used more effectively, fires are put out more rapidly, said Crawley. CAFS foam sticks to combustible surfaces, meaning more protection for those battling the blaze.
"If the water is in the basement it doesn't put out the fire," Crawley said. "When you are looking at anybody's statistics about a conventional water-fire protection system, you're looking at 90 to 95 percent of the water ending up in the basement.
"We have done a number of house burn demonstrations with CAFS where you can walk around down in the basement and not even get your boots wet, said Crawley. There may be a quarter-inch of water in places on that floor but the whole floor will not be wet. It is not uncommon to use less than 100 gallons of water to put out a house fire."
Less water used also mean less water damage to the home and contents in extinguishing the blaze, the manufacturers agreed. Companies investing in CAFS technology need to understand the changes involved in everyday fire fighting, said CAFS pioneer Mark Cummins of Cummins Industries.
"When your incident commander sets up a fire operation he's been well trained with water handling," Cummins said. "The water trucks shows up and the attack evolves. But when you get a CAFS truck on the scene everything changes -- the tactics of actually fighting the fire, the effects of the runoff, everything."
When water and air is mixed, the result is hollow spheres of water known as bubbles. These spheres are by nature unstable, collapsing quickly. By adding foam concentrates containing surfactants, the surface tension of water is reduced. This allows small, uniform bubbles to form.
"If you take a droplet of water and you turn it into a bubble, you increase the surface area of that water. So you get maximum cooling effect in fire fighting," said Guse at Odin.
Air aspirated foam produces a bubble much finer than ordinary detergent but still big enough to see. The bubbles are also much more stable so they do not break apart when hurled through a nozzle. CAFS produces a bubble structure that is almost microscopic by comparison to air aspirated form. Lather might be a better word to describe it. In terms of durability, the thick foam lingers longer than the last guest as a wedding reception.
"You get a nice frothy uniform foam," Guse said. "Shaving cream is relatively dry but it is a good comparison. By doing this you get a better bubble structure."
How does something usually associated with kids playing in the bath tub become a life or death matter for firefighters? When foam is applied to flames, water is slowly released as it breaks down. This water increases in temperature, absorbing heat as it turns to steam. This robs the fire of energy and extinguishes it. Since the water is released at a slower rate than directly applying it to the fire, none of it is lost as runoff. Because of the decreased surface tension, the foam readily adheres to almost any vertical or inverted surface. When applied to threatened exposures it will act as an effective insulation, the water released by the heat acting to cool the surface.
"It's so lightweight," said Paul at CFX. "The heavier it is the faster the water pulls the foam down. We have even foamed glass." Compressed air foam shares one more characteristic of shaving cream. It is extremely white, which makes it extremely heat reflective, said Grady at Pierce.
"You have a double negative for heat in that you have a bubble structure that is insulation and then you have the white surface," he said.
A third negative would be penetration. Guse said the increased surface tension provided by the added surfactants means that the water content of the CAFS foam penetrates more deeply into the burning fuel.
"It's just like water and your clothes when you wash them," he said. "Sudsing detergent is a surfactant and it allows the water to penetrate and lift the dirt out. Say there is a fire in your living room. You spray water on the couch but it is treated with a stain resistant finish like Scotchgard?. All the water runs right off. By putting a surfactant in the water such as foam it allow the water to penetrate and soak in."
Compressed air foam is so thick and rich that it often short cuts the entire process by shutting off its oxygen supply and smothering it outright. When applied correctly, the foam provides a vapor seal regardless of what class foam is used. That means added reflash protection, said Mahrt at Tri-Max.
"So when we shoot it at a fire it not only puts the fire out, such as flammable liquid or toxic chemical or hazardous material, even metal fires, but then our system keeps working," he said.
The fine bubble structure expected from CAFS is available using any fire foam product on the market, Mahrt said. With air aspirated nozzle systems, Class A foam agent is proportioned at an application rate of .5 to one percent. Class B AFFF foam agents are proportioned at three to six percent, depending on whether it is a hydrocarbon or polar solvent involved. Compressed air foam performs its magic at a normal application rate of between .3 and .5 percent. Some manufacturers brag they have pushed to a rate as low as .1 percent using Class A foam concentrate.
"It is such an efficient way to make foam," Cummins at Cummins Industries said.
"You use less concentrate so it is much more economical than aspirated foam or the eductor type foam systems. Standard Class B foaming agents use three to six percent, meaning roughly you've got to have roughly three gallons for every hundred gallons of water. Compressed air foam systems start at about two-tenths of a percent and makes at least 10 times more foam than an aspirated system. There is actually no comparison."
Grady at Pierce said that testing CAFS to determine the correct application rates can be a surprising experience.
"Your critical application rate for a given fuel tends to be half again lower than the critical application for a conventionally applied foam," he said.
"We did some preliminary testing at Ansul using the standard UL 162 foam test calling for a two gpm nozzle. We established a base line for the particular fuel using conventional aspirated foam, then we would use the compressed air foam generating method. With a one gpm application rate we still put the fire right out and in the same extinguishment time if not sooner.
"We used so very little foam to gain extinguishment that every so often there wasn't enough there for the burnback test. The chemists were looking at what you could do if you took compressed air foam applications farther forward. Would you cause the finished foam to drain less so there would be more left when you got extinguishment? Or would you look at the test and say 'Don't shut off instantaneously at extinguishment as you do now -- clock the extinguishment time but then put a bit more on for securement.' That has been the one question that has come up."
The reduced application rates are not the only thing that gives some firefighters pause. Compressed air foam is most effective when used with a smooth bore nozzle, period. Any type of nozzle that obstructs the most direct route between the hose and the fire defeats the purpose.
"Most nozzles in one form or another try to break up the water stream coming out of a hose into smaller pieces or particles," said Guse at Odin.
"Say you've got garbage burning in a barrel. If you spray a big stream of water at it, the water splits up and most of it just runs off. If you break it into a real fine mist it tends to cover the fire better and cool it much faster. And so that's why you try to use a fog nozzle to break up the water."
A firefighter still has the option of using an adjustable fog tip with a CAFS unit, said Geary Roberts, president of Pneumax, a division of Waterous. Like Hale, Waterous is a major manufacturer of pumps used by the fire service. The problem with fog nozzles, said Roberts, is that the teeth strip the bubbles out of the compressed air foam.
"You still get the advantage of real light weight hose, because there is mostly air in there, but you get a lot wetter foam," he said. "With a smooth bore tip you get the full advantage of compressed air foam. You get a nice tight growth of small bubbles which we believe is the most finely divided water particle that you can introduce into a fire atmosphere and get rapid steam conversion."
Fighting a structure fire with a smooth bore nozzle on a CAFS unit can be every bit as effective as the fog nozzle, Roberts said.
"We've seen it where a smooth bore CAFS stream is introduced into the first floor of a two-story, fully involved house and both floors extinguish immediately."
The size nozzles that firefighters use with CAFS systems are grossly bigger than what would be used for water alone, said Colletti at Hale.
"There are different dynamics involved and different procedures that need to be followed when using CAFS," Colletti said.
"We take the firefighter who is used to a 15 degree fog nozzle for interior attack and in training give him a CAFS using a smooth bore 13/8-inch nozzle. They tend to be concerned."
At Pierce, Grady said he recommends a one-inch to 11/8-inch straight tip nozzle to produce a wet foam that stays longer on hot surfaces. For dry foam, Grady said the tip size should be increased to 13/8-inch to make a long-lasting, slow-draining dry foam as used in protecting an unignited exposure.
"What occurs is you lower the nozzle pressure or slow the exit velocity," he said. "More of the bubbles don't pop as they come out into the atmosphere. And the foam stays firmer or what we call dryer. The smaller nozzle actually pops some of the bubbles and liberates some liquid that goes along for the ride.
"On fire knockdown you typically want to go ahead and pop the bubbles to give you that mixture of almost free solution for filming or cooling effect. It hits the fire quickly and then it's pretty wet, very fluid foam to cover up and secure."
Aside from the bubbles, a firefighter who prefers a wetter foam also sacrifices reach. A fire nozzle is basically a venturi, i.e., a short tube with a constricted section at the center that lowers the pressure and increases the velocity of the fluid flowing through it. However, a CAFS unit depends on pressure from its air compressor for its reach. A constricted nozzle that strips the bubbles out of the foam also strips the energy out of the stream.
"You've seen what happens when you put a foam nozzle or an air barrel on the end of a line," Grady said. "Stream reach goes to heck. CAFS typically can throw a better foam about twice, sometimes 21/2 times farther than an aspirated nozzle. Usually CAFS can easily get it out there as far as a regular multiple pattern nozzle. But it's a finished foam. It will throw a finished foam that far."
For those who still want the option, several manufacturers recommended using the Akron Saberjet, which has an adjustable fog and smooth bore incorporated into one nozzle.
Beyond the choice of nozzles, the one issue assured to create controversy even among the proponents of CAFS is the choice of foam -- Class A or Class B.
Some insist that the old distinctions between different classes of foam are largely irrelevant when talking about CAFS. Class A foam, primarily used in structural fire fighting, is formulated to spread and penetrate. Class B, used in flammable liquid fire fighting, floats and smothers. Other experts warn that applying foam intended for a specific type of fire indiscriminately is asking for trouble.
Crawley at Snuffer cites extensive live burn testing for his claims about CAFS foam.
"We have probably done more live burn work than anybody else because the regulations in Canada are less stringent than the U.S," he said. "At this point our recommendation is that on a fuel spill fire, if it is not a situation where you are going to have to be going into the fire, you can put it out just as effectively with Class A as an AFFF.
"What you can't do with a Class A like with a Class B is if you're going to be walking in it. It doesn't heal up like a Class B. In that case it is not effective."
Research on the use of CAFS in fires involving hydrocarbon fuel in depth, as opposed to spills, is ongoing, Crawley said.
"We have tested at the Underwriters Laboratory, the UL 162 hydrocarbon in depth tests, and on scale CAFS does cut the application rate by 50 percent," he said "The question is going to be how hard it is to scale up an application system up in the field."
Roberts at Pneumax also said he believes Class A foam can be safely used against hydrocarbon flammable liquid fire.
"We don't advocate the use of it with anything like alcohol or polar solvents," he said. "For that you still need alcohol resistant concentrate. The reason that Class A compressed air foam is effective on hydrocarbon fuel fires is because of the bubble structure. You've got very small, tight bubbles with a very strong bubble wall. So it makes a good vapor barrier. You flow a vapor barrier over the fire in the form of a foam blanket and you really don't need that film you get with AFFF (aqueous film forming foam). But alcohol, ether and polar solvents just eat it up as they do straight AFFF."
Cummins at Cummins Industries said that strong bubble structure can be produced just as well using dish soap.
"That struck a cord with many of the industrial firefighters who started off in the early years saying 'You're going to get somebody hurt trying to use dish soap or a Class A foam on Class B fires,' he said. "If it's dense durable foam it does matter what you make it out of. It's the vapor sealing characteristic that you are looking for to put out the flammable liquid fires.
"We are changing the tactics of using foam. The small bubble structure is so durable that instead of using just a gentle blanket on the top of the fuels we are actually emulsifying the surface fumes. We use a much less gentle application to mix it with the fuel. If you've got fuel running across the driveway, instead of a gentle floating cover on the surface you shoot hard trajectory right in front of it and mix all the fuel into the foam. Then the foam breaks it into its individual molecules and suspends them inside the foam. They can't get to the oxygen. So you literally emulsify the running fuel and stop it in place. Then you can dike the foam or vacuum it, however you're going to treat it."
What makes CAFS using any kind of surfactant, dish soap or Class A, preferable to Class B aspirated foam is the amount of water the later requires, Cummins said.
"The inefficiency of current foam systems still require tremendous volumes of water," he said. "If you're flowing 10,000 gpm into a storage tank you are filling that tank at that rate. The majority of your foam drops out in that sort of drain time in just a couple of minutes. That goes to the bottom of the tank causing the tank to overflow. So you try to fight the fire with as much as they can as quickly as you can.
"It is the exact opposite of CAFS. Our foam doesn't break down and doesn't drain. Put this foam in and it stays over the surface. Any overflow you get is foam overflow. None of it goes to the bottom of the tank."
Cost more often determines what firefighters use to extinguish a fire, not what manufacturers recommend, said Ludnicky at Neel.
"You start getting into Class B and AFFF and you are talking about some heavy dollars real quick," Ludnicky said. "The big problem is you get into some of these little rural communities or any of those small towns with their volunteer departments, they can't afford $60-$70 a gallon foam to put out a grass fire. They are going to draft out of a stock tank somewhere if they can find one."
At Odin, Guse said industrial fires such as flammable liquid storage tanks should always be fought using the appropriate foam. However, Class A foam has successfully been used against hydrocarbon spill fires by local fire departments, he said.
"You can use Class A foam, CAFS, on fuel fires, as long as they're not alcohol based, because the foam will still float on diesel or gasoline," Guse said. "But it doesn't have the healing effect the Class B foams do. So you have to temper how you use it.
"In South Carolina a fire department and pulled up on a 6,000 gallon tanker fire. The fuel was running in the ditch. It was burning across the road and out into the woods. They did the knockdown and blackout with 1,000 gallons of water. For fuel spread out like that is pretty darn good. They used Class A foam on that. They just floated it over the top, took away the oxygen and, boom, as long as there is not another ignition source, you knock it down."
CAFS can effectively be used against a hydrocarbon fire in depth such as storage tanks, as long as the recommended type of foam is used, Guse said.
"You can use CAFS but you would definitely need to use a Class B type of CAFS," he said. "The reason is the healing property of the foam. As it drains down it creates that film. But with Class B CAFS you still want to put a little aspiration to it.
"You can still use Class B CAFS for exposure protection. Say you've got two tanks next to each other. You're spraying the Class B on the fire and trying to put it out that way but there is a tank right next to it. You turn up the application rate and you put Class B CAFS on there. It will create a nice bubble structure too, in a lot of cases almost as good as a Class A, because Class A foams really nice."
Using CAFS on a fuel tank fire means a much more durable, sturdier foam blanket, Breedlove at Intelagard said. The result would be better vapor suppression with a lot less foam agent. However, firefighters being trained on the use of CAFS should get experience using all types of foam, he said.
"For instance, our training up in New Jersey involves different types of Class A and Class B fires," Breedlove said. "I'll have six or seven different foam agents with me, and I'll use all of them. Some of them are UL listed AB, some are strictly A, some are B, some are hazmat remediation. But they all work well through our CAFS. It just depends on the type of fire you're fighting."
Like Guse, Breedlove said that Class A foam used through a CAFS unit is just as effective as Class B in extinguishing a hydrocarbon spill fire. And, also like Guse, he said that only Class B foam should be used to suppress the vapors on a fire involving a hydrocarbon pool.
"The A foam doesn't heal and it doesn't have the polymers in it to recreate the aqueous film over the surface of the liquid."
Colletti at Hale said statements regarding the effectiveness of CAFS units when using foam other than the class recommended by the foam manufacturer should be carefully considered.
"One of the challenges this industry has is the transfer of information," Colletti said. "You have to watch out for bad information. I have put out some very small pan fires using Class A foam. I've fought flammable liquid fires with Class A compressed air foam. Nevertheless, you need to use the best product for the application. If in doubt, you should use Class B compressed air foam on a flammable liquid fire at the published application rates."
What people report based on live fire demonstrations can sometimes be deceiving, said Al Ozment at U.S. Foam. Attempting to extinguish a flammable liquid with the wrong class foam is not worth the potential loss of life or property, he said.
"I went through rookie school in the fire service back in the mid-1970s," Ozment said. "When we were training we would flood a low area of the training field with water, pour gas on it and fight that with straight water. Of course, the way we extinguished it was to basically push the fire off the fuel.
"Sure, you could put a Class B fire out with a Class A product but I think the hazard and the danger is not worth the risk. There are no film forming properties in Class A foam. It doesn't suppress vapor. And if that foam blanket breaks you've got a reignition potential. AFFF is designed to suppress vapor even without a foam blanket."
In post 9-11 America, CAFS technology has found new and important applications. U.S. Foam is one of only two companies licensed to manufacture a foaming solution developed by Sandia National Laboratories that has proven to decontaminate and neutralize every biological and chemical weapon known.
"You don't have to determine if the hazard is biological or chemical," Ozment said. "The big selling point is that it works indiscriminately." And, as it turns out, the best way to apply this foam is using CAFS units. Intelagard is only one company who has sold CAFS equipment for this specialized use.
"By generating that same durable, uniform bubble it allows us to get the foam onto surfaces," Breedlove said. "You maximize your wet contact time and lessen your drain time by making stiff foam.
"The Army's Soldier Biological Command has purchased around 35,000 gallons of this formula. So it has gained a lot of acceptance and is a growth industry, unfortunately."
CAFS units were used to decontaminate postal facilities in Washington, D.C., during the anthrax outbreak that followed the Sept. 11, 2001, terrorist attacks on the United States, Ozment said.
"The proportion ratio is typically 25 percent but most proportioning systems won't go that high. Usually what we do is batch mix (pour foam concentrate directly into the water tank), then use compressed air foam," Ozment said. "Of course we have that third component which is compressed air injected into the line to give it the expansion ratio. It works extremely well."
Tri-Max, which already had close ties to the military, is specially adapting its equipment for decontamination use. "We have a vapor suppression unit called Tri-Max VSU," Mahrt at Tri-Max said.
"We've devised a way where we can get our ratio up to 50 to 1 expansion and still project it over 50 feet. We are now working with a couple of different companies that have UL approved chemical compounds that both suppress fires, suppress vapors, also biodegrade to neutralize a spill. It doesn't have to be cleaned up, you just wash it away. When we put it into our vapor suppression unit it's the perfect initial response for biological warfare or hazardous materials spills, chemical spills, materials that are either toxic or volatile and flammable."
EZ Decon also has a strong reaction to toxic industrial chemicals and could be applied to hazardous materials remediation, Ozment said. Another product along those lines brought Texas-based Cummins Industries together with a chemist at the Naval Surface Warfare Center in Dahlgren, VA.
"I was working with Mark Cummins because I had developed a chemical-biological agent decontamination formula," said Dr. Donald Cronce. "I linked up with Mark because he had the equipment I needed. His CAFS unit was able to produce a foam with a formula that I had patented."
Cronce is in the process of licensing his invention, a formula that breaks down organo-phosphate pesticides such as Malathion, Peraoxon and others.
"The components in the foam react with the pesticide itself," Cronce said. "Essentially, concerning those reaction mechanisms, the byproducts of these reactions take away the hazard of the pesticides."
Cummins said spills involving organo-phosphates frequently occur in industrial settings, particularly along the Houston ship channel.
"Our CAFS unit has been selected as the application method because it gives an even distribution and holds the reactive ingredients in contact with the toxin long enough for it to have an effect."
Other types of bioremediation using CAFS units may yet prove to be an important source of future revenue for small fire departments across the country, Cummins said.
"Texas state environmental regulators will allow bioremediation as a satisfactory solution to spills," he said. "Some of the fire departments are adding the dry microbes to their foaming agent and then charge the insurance companies for the cleanup. It is no longer a non productive expense for the fire department. They are making money by charging for the emergency response spill cleanup instead of calling a professional service company."
By adding a stabilizer to the product, fire departments will have a new tool in dealing with cleanup following structural fires, Cummins said. It could also become still another new source of revenue.
"Ash is full of listed toxic byproducts," he said. "When we go to a house fire or an industrial fire that has a large amount of ash instead of letting that ash blow around the neighborhood we are covering it up with CAFS foam to keep it in place. The stabilizer in the foam settles down to seal the surface permanently. When the demolition team comes in or the investigators start moving the ash it doesn't blow around."
The Joshua Fire Department, near Cummins' home, handles bioremediation in car wrecks with a Cummins CAFS unit, recovering about $1,000 per car, he said. Another recovery expense the department charges is $1,200 for structure fire stabilization. The department charges $750 for use of the fire engine that creates the foam, plus manhours involved, Cummins said. The applications of CAFS technology for homeland defense is immediately apparent, Cummins said.
"Homeland defense is going to require extraordinary equipment to handle a threat such as a powdered, toxic substance that is a chemical and a biological agent," he said.
"One of the things your first responder is going to have to do is create a hot zone and secure it. If it is a powdered substance or a vaporizing substance you're going to have to seal it with CAFS foam. It will stay for days without any runoff."
Breedlove at Intelagard said decontamination and bioremediation are just two more fire service tasks that make the multifunctional CAFS a good buy for fire departments.
"Say there is a resistance to purchasing a specialized piece of equipment to do hazmat," he said. "This is a piece of equipment that because of its ability to use all these different agents and, in effect, enhance the agents, can do fire fighting, exposure protection, hazmat response, biochemical remediation., all with the same piece of equipment. So that is a great benefit."
But while decontamination is a growing concern, sales of EZ Decon have been a little slower than projected, Ozment said.
"I think the reason for that is because most of the municipal (fire service) business is just a little gun shy," Ozment said. "There are always new products that come out and go away very quickly. I think the municipal fire service likes to stand back for a while and make sure that a product is proven and make sure that it is going to be around not just today but for tomorrow and the next day and the next day before they really jump on the band wagon.
"The projection hasn't been as good as what we expected but the growth is very good. It's steadily increasing I think because of the military use. The military is using this product pretty widely and that in itself is giving more credibility to the product. The fire service tends to thrive on credibility."
For CAFS to ever approach the success of air aspirated systems an entire generation of firefighters must reprogram their thinking about the use of some of the most basic fire fighting equipment at their disposal. Change often goes against the grain in the fire service. The proponents of CAFS technology remain resolute in their crusade. Education is what is needed to take the mystery out of this foam alternative, said Colletti at Hale.
"Many departments are very low on the educational curve regarding what they need to specify when ordering a CAFS unit, how to use it and under what conditions," Colletti said. "This is very different tactically from plain water application. We have a big education job to do on virtually every aspect of CAFS."