Fire Department, Special Operations Hazmat, Wildland Urban Interface

Compressed Air Foam Systems Are Starting To Gain Momentum

Issue 4 and Volume 12.

The oversimplified adage used to call for “putting the wet stuff on the red stuff.”

These days, there’s an updated version: Put the white stuff on the red stuff, the “white stuff” being compressed air foam – a combination of water, foam concentrate and compressed air – which proponents say provides quicker knockdowns, uses less water, cuts fire losses and offers a host of other benefits beyond those of just water.

“It’s not a substitute for water flow; It’s not a substitute for manpower,” said Bill Ballantyne, vice president with FoamPro, the Minnesota-based makers of foam proportioner and refill units. “You still go in with the same water flow. You still go in with the same manpower. It just makes your job more effective.”

Compressed air foam systems, known as CAFS, are not new. They have been around in various forms since the 1930s, but today’s systems are nothing like those of old. They are easier to use, more reliable and less expensive than those produced just a decade ago, and they are seeing more use in structural firefighting after early adoption for wildland applications.

And, as the systems have improved, so have the prices, though they can still vary widely, from $30,000 to more than $40,000, depending on the manufacturer and the system’s specifications. Today, many pump and apparatus manufacturers offer a CAF system.

“It’s beginning to catch on more,” said CAFS proponent John B. Gill, of Katy, Texas-based Fire Fighters Tool Co. “The problem has always been that it’s been kind-of spread word-of-mouth by the manufacturers. Some did a good job. Some didn’t do such a good job.”

So, last year Gill organized the first Southwest CAFS Symposium, to provide education about CAFS. That event drew about 175 people. This year’s symposium, held Feb. 9-11 in Rosenberg, Texas, southwest of Houston, counted 240 participants, including CAFS experts – fire chiefs, manufacturers’ representatives, users and others interested in the technology.

“I got really tired of all of the misinformation that was being passed on about CAFS,” Gill said. Among the popular misconceptions, he said, were: that firefighters would get burned if using CAF on an interior attack; that CAF systems use no water; that CAF pushes the fire through the structure because of the compressed air; and that CAF does more damage than water.

“We looked all over the country, and we couldn’t find any place where a fire chief or fire department could go and get all of the information,” Gill said.

Someone interested in CAFS could go to manufacturers or occasional classes, but Gill said he found no single clearinghouse with CAFS resources. This year’s event featured a series of speakers on topics ranging from CAFS history and its basics to training, technology and tactics, with part of the event devoted to hands-on use of CAFS units.

“We really estimate we’ll be over 300 people next year,” Gill said. He expects the seminar to grow as CAFS technology catches on, as the benefits become more widely known and as the systems draw more interest.

CAF proponents site a long list of benefits, including: improved firefighter safety; improved efficiency of water and less water use; faster knockdown times and fewer rekindles. Because CAF uses less water, there is decreased property damage and better preservation of evidence, less runoff, faster cleanup and reduced time on-scene.

Cutting Fire Losses

“You can immediately reduce your fire losses by 50 to 75 percent,” Ballantyne said. “What other initiative would have the same impact? If you’re not considering it for your department? Why?”

The technology is now getting more attention, but CAFS has been around for some time.

Early systems were used in the 1940s by the British Royal Air Force and the U.S. Navy for flammable liquid firefighting, according to Dominic J. Colletti, foam products manager for Hale Products Inc. Colletti is also one of the nation’s leading proponents of CAFS.

Those early systems, typically for shipboard use, operated using principles similar to today’s systems, Colletti said. As they were typically used on flammable liquids, they might be considered similar to today’s Class B foams.

By the early 1970s, a new generation of the technology emerged when the CAFS forerunner known as WEPS – Water Expansion Pumping System, which also used compressed air – attracted the attention of the Texas State Forest Service for wildland fire use. By the late 1980s and early 1990s, the systems became more commercially available.

Technology Improvements

“They were really held back because the technology wasn’t available for the type of foam or injection systems, the compressors or the synching systems,” Gill said. “They worked, but they didn’t work all of the time.”

Today’s systems, for example, automatically set water and air pressures – previously a task done manually – and foam proportioner systems themselves are considerably more accurate, making it easier to make the correct foam. Additionally, the foam concentrates themselves have improved.

“It has been amazing to watch the transition, as these units were not user-friendly, and today, they’re very user-friendly,” said Marvin O. Johns, South Central U.S. Regional Manager with Hale Products Inc. “Technology has brought us a long way. The interest out there is unbelievable at this point.”

But even since the early days, a CAF system has generally operated with similar components: water and pump; air compressor; and foam concentrate, along with some way of introducing the foam into the water stream. That’s accomplished by using a foam proportioner, which handles the task with considerable accuracy.

Explanations of the components of CAFS follow:

Water and pump: As with standard firefighting practices, water can come from on-board supplies, municipal systems, drafting or from any number of sources. CAF systems also work with pumps of various sizes, and several pump and apparatus manufacturers offer some type of CAF system.

Air compressor: Simply put, the compressor generates the air that is fed into the hoseline. Typically, these are rotary-screw type compressors capable of high-volume output, typically as much as 220 cfm or more, and they can be pto-driven, hydraulically driven or driven by an auxiliary engine.

As the number of discharges on an apparatus increases, so does the required output from the compressor. Additionally, the compressor can be used to supply air for other fireground needs, such as running air tools or inflating rescue bags, even while a hoseline might be flowing foam.

Fixed Air Supply

Not all CAF systems, however, require a compressor. Hale’s CAFS Attack system, for example, uses a fixed air supply featuring two compressed air cylinders, which store 880 cubic feet of air, can be installed in new and retrofit applications and can be refilled using typical compressed air systems used to fill SCBA bottles.

Class A foam concentrate: CAF systems use Class A foams, suitable for use on Class A fires of ordinary combustibles, such as wood, paper, rubber and other common materials. In structural firefighting, Class A foams can be used for initial attack, overhaul and exposure protection. They are also suitable for wildland applications.

Class A foam concentrate is made from a blend of “surfactants,” a term for agents found in things such as cleaning products. The concentrate itself is similar to high-grade dish soap or industrial cleaners.

At its basic level, the concentrate allows the water and air to mix, reduces the surface tension of the water and – by creating additional smaller “bubbles” – increases surface-to-mass ratio. That allows for greater heat absorption.

“It’s effective in all phases of the operation,” said FoamPro’s Ballantyne. “The key thing is the wetting agents and the Class B concentrates not be mistaken for the Class A foam.”

In short, that’s because both types of foams serve different purposes, and they also work differently. Class A foams, originally developed for wildland use, are designed to work on ordinary combustibles, while Class B foams are used on liquid fuels.

Made from a blend of surfactants, Class A foams penetrate Class A fuel surfaces and are good for wetting and cooling fuels, suppressing flammable vapors and reducing smoke. They also collect on surfaces, reflect heat, create insulating bubbles, and are biodegradable.

Class B foams, meanwhile, are used to extinguish liquid fuels. They smother the burning liquid, causing a vapor barrier that separates the fuel from oxygen.

Foam proportioner: Early CAF systems featured many of the same components found on today’s systems, but metering the correct amount of foam introduced into the water stream initially proved tricky.

“The proportioners drove us nuts,” says Clarence Grady, who was involved with early CAF systems and is now foam system manager with Pierce Manufacturing of Appleton, Wis. “You could figure on them conking out.”

Today’s proportioners, however, more accurately inject the correct amount of foam into the fire stream. The electronic units measure water flow, then send that information to the controller and on to the injector. Pump-based proportioners with direct injection are popular, Ballantyne said.

“Having a dependable proportioner is an important part of making good compressed air foam,” Colletti said.

Another CAFS benefit is the ability to make finished foam wetter or dryer for different applications. By reducing the percentage of foam concentrate in the hoseline, the foam becomes wetter, making it ideal for initial attack or overhaul; a dryer, lighter foam, meanwhile, can be used for exposure protection as it clings to surfaces.

Hose and nozzles: Of course, none of these components help if there isn’t some way to put the foam on the fire. As with traditional water-only operations, hose and nozzles also play a part in the equation.

“There’s not an official CAFS hose,” said Pierce’s Grady. All conventional hose of conventional diameters works with CAFS, though he has seen some lightweight forestry hose develop leaks because the thin polymer liner cracked, allowing foam to get between the liner and the hose jacket.

“I never saw that effect on standard rubber-lined, double-jacketed and that’s what everyone’s using,” he said. “With a rubber-lined, double-jacketed standard stuff, it’s never really had any real issues. And standard diameters have been good.”

Additionally, foam doesn’t require a special nozzle, either, according to CAFS experts. They do, however, have their preferences.

“To a certain extent, there isn’t a nozzle that absolutely will not work,” Grady said, though a high-pressure fog nozzle can strip air from the stream, making the foam wetter. “Each nozzle will have a certain effect on the foam. A straight tip’s probably more effective.”

FoamPro’s Ballantyne also recommends a smoothbore, but combination nozzles have also been effectively used.

“The nozzle that you use is an important part of the entire integrated system,” said Hale’s Colletti, who also prefers a smoothbore nozzle, but noted that training considerations also play a factor. “As an end user, look at all the nozzles out there and decide what’s best. There’s a whole bunch of limits and advantages no matter what nozzle you pick.”

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