FIRE INDUSTRY TODAY Norbe Puroll
With 36 years of experience in the fire safety industry, I frequently encounter the misconception that “Foam is expensive to use.” This is simply not true.
Both Class A and Class B firefighting foams are cost-effective and, more importantly, enhance firefighter safety and efficiency. These foams are valuable in effectively extinguishing fires, helping firefighters to better protect property and save lives.
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Class a Foam
According to the National Fire Protection Association (NFPA), Class A fuels include materials such as vegetation, wood, cloth paper, some plastics, and rubber. This includes vehicle fires and nuisance fires like dumpsters, tire, and trash piles.
Class A foam is specially formulated to make water more effective for firefighting. The surfactants in Class A foam significantly reduce water’s surface tension, which penetrates the fuel. The foam creates a barrier between the fuel and the fire, knocking down the fire faster than water alone. The foam’s visibility also makes it easier for firefighters to see where the product was applied. Water draining from the bubbles continuously cools the fuel, which lowers the chance of a rekindle. This increased water efficiency reduces the amount that is needed to extinguish the fire. At the use levels required, one gallon of foam concentrate used at 0.1% can generate 1,000 gallons of effective foam solution. This reduces water damage to the property owner, results in less water being sent to wastewater treatment, and lowers runoff ground contamination.
Quicker knockdown reduces mop-up/over- haul requirements. The sooner a firefighter gets off the fireground, the less chance of him being injured. It also reduces firefighter and neighboring communities exposure to potentially carcinogenic products of decomposition. With the change in interior construction materials from wood to plastics, flashover decreased from 25 to 30 minutes to 3 to 5 minutes. The sooner the heat is lowered, the greater the chance we have of creating tenable space for a better work environment for firefighters. More important, there is an improved chance to save victims. When foam is used in a rural setting where there is a water shuttle, less water is needed, so you lower the chance of an apparatus accident while going to and from a fire scene hauling water. Therefore, fewer water shuttle trips may be required. These are unrealized cost savings. By cutting the time on a fire, fuel cost is lowered, and wear and tear on your apparatus is reduced, leading to less scheduled maintenance and longer apparatus life.
When mixed with air, Class A foam creates a thick foam blanket that surrounds fuels, creating a barrier between the fuel and the fire. This is valuable in protecting structures adjacent to a fire. For vertical exposures, a foam blanket will reflect radiant heat, allow the exposure to absorb water for prolonged protection, and help insulate the surface.
Class A foam also introduces advantages when battling tire fires, which are among the toughest fires to extinguish. Water alone on tires simply beads up and rapidly rolls off, but the reduced surface tension of Class A foam allows water to cover the tire surface, penetrating deeper into the piles.
Some additional benefits of Class A foam:
- Reflects radiant heat and is highly visible.
- Insulates fuels and excludes oxygen.
- Absorbs maximum British thermal units due to its large surface area.
- Clings to vertical surfaces to insulate and act as a water reservoir.
- Penetrates water into fuels because it lowers surface tension.
Class a Foam Testing
Several studies demonstrate the benefits of using firefighting foam. In 1992, a series of tests called the Salem Tests were conducted to compare the effectiveness of water, foam, and compressed air foam systems (CAFS) in reducing temperature. They measured the temperature drop from 1,000°F to 212°F at a 4-foot level.
It took 223 seconds for water to achieve this reduction. Adding foam reduced the time to 103 seconds, and using CAFS dropped it further to just 39 seconds. Another series of tests in 1999 included a crib burn test under controlled conditions, testing Class A foam vs. plain water. Results indicated that 40 percent less water-foam solution was used than plain water. There was 43% less extinguishing effort with foam than with using just water.
In August 2021, the Los Angeles County (CA) Fire Department conducted the Palmdale Study, which tested the use of Class A foam on homes. The homes were all built the same and were scheduled to be demolished. The department found that it took 73 gallons ofwater to put out a specific type of Class A fire. With the addition of foam, the amount of water required fell to 44 gallons, and using CAFS further reduced the amount of water needed to 16 gallons.
The fire department also took temperature readings via wall- and ceiling-mounted thermocouples at one-foot increments. These tests showed that it took six minutes on average for water to bring down the temperature of a fire from 600°F to 200°F. Once foam was added, the same temperature reduction was achieved in one minute 45 seconds. This significantly increases the survivable space for firefighters and occupants.
Class B Foam
Class B fuel fires are hydrocarbons or polar solvents. Class B foams used to battle these fires are proportioned at different rates based on the product used. If a product only has one number on it, the number indicates the setting on the proportioner to battle a hydrocarbon fire: 1%, 3%, or 6%. Polar solvents require alcohol-resistant (AR) foam. These fires require a dual-numbered product: 1% x 3%,
3% x 3%, or 3% x 6%. The first number is the percent setting for hydrocarbon fire and the second number is for a polar-type fire.
Different types of Class B foams are engineered based on exposures. These can be industrial type fires like refineries or tank farms, used in aircraft rescue and firefighting (ARFF) units for military aircraft or airports,and contained systems with sprinkler heads or polar (alcohol)-based fires.
The old aqueous film forming foams (AFFF) were designed to form a film, sealing vapors. The new synthetic fluorine-free foams (SFFF) are designed to make a blanket to seal vapors. Application style is different than AFFF. There are several different techniques used to apply SFFF based on how the fire presents itself. These are roll-on, horizontal-spray, bounce-off, or rain-down.
Fluorine-Free Application Techniques
If a straight stream is sprayed using SFFF into burning product, it plunges, bringing product to the surface. That leads to ghosting, emulsification, and foam blanket contamination. You can tell it is happening as the foam changes texture running in channels. If it is burning underneath, it looks like a mole tunneling under the blanket. You will have to apply more foam with a horizontal or a rain- down method. SFFF does not seal or surround objects like AFFF did. You may need to reposition yourself to cover the whole area. When two blankets come together, it makes a seam and will not seal. Here you use horizontal or the rain-down method to stitch the seam together.
Final Pointers for Using Foam
- Fire is red, foam is white. Paint the fire! If it is white, it is wet! Shut off the nozzle and let the foam do its work. If it’s still red, paint it some more. You create less water damage.
- Fight fire the same as using only water. You will see quicker knockdown and suppression.
- Add a foam tube to your nozzle to make a better blanket.
- If you change foam brands, recalibrate the system, as they may have a different centipoise (viscosity).
- Do annual maintenance on your foam system.
- If you buy a new apparatus, after using the foam system for a while, check the wye strainer. It may have plastic particles in it from when the tank was plumbed. Perimeter Solutions offers a complimentary three-hour course titled “Know Your Foam.” This course aims to improve departmental efficiency in using foam during fires, enhancing the chances of saving lives and property. Attendees learn the cost savings associated with foam use and how and when to use Class A and Class B foams, emulsifiers, and retardants. Foam systems, manual eductors, nozzles, expansion tubes, and application techniques and rates are also covered. The course includes a practical session on flowing foam. Perimeter also offers an SFFF training session on ARFF for airports.
NORBE PUROLL leads business development, government and municipal, at Perimeter Solutions. He has worked in fire safety for 36 years, 18 as a volunteer firefighter/EMT. Prior to joining Perimeter Solutions, he was a regional manager for a large apparatus component parts manufacturer.