Your Guide to Firefighting Foam: 2024 Edition
Firefighting foams have become a hot topic in the fire service as local, state, and national governments implement new regulations about the use of Aqueous Film Forming Foams (AFFF). Few are immune from new regulations as even the US Navy must publish a new military specification for use of fluorine-free foam and make a transition by October 2024.
Understanding firefighting foam, the changes, and your options can help you make the best decision for you and your department in the coming months and years.
With that in mind, here is our guide to firefighting foam.
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What is Firefighting Foam?
Firefighting foam was developed more than a century ago to fight oil fires that were problematic to water application. Today, it is used to knock down and secure burning and unignited flammable liquids.
Firefighters use foam for several reasons:
Improved extinguishment time
Creating a physical separation to exclude oxygen from flammable vapors
Removing heat from a liquid and surrounding surfaces
Creating a vapor barrier to prevent vapor from escaping upward
Lowering the surface tension of water allowing it to penetrate more deeply into fuel
Featured Article: What is Firefighting Foam and Why do Firefighters Use it?
How Does a Firefighting Foam Eductor Work?
To successfully apply firefighting foam, you will need an eductor. These devices work using the Venturi Principle. This principle uses extreme pressure loss inside the eductor to allow foam concentrate to flow up a pickup tube and into your water stream, creating a foam solution.
This eductor is vital to proper foam proportioning and ensuring good quality foam.
Featured Article and Video: How Does a Firefighting Foam Eductor Work?
Finding Your Size and Type of Foam Eductor
There are a few things to consider as you select your size and type of foam eductor. For the best experience, confirm these four things:
Your eductor flow rating matches the flow rating of your nozzle.
You have a proper length of hose between the eductor and nozzle
Your nozzle is open all the way and not gated
Whether you need a foam attachment to entrain air
Featured Article and Video: What Size and Type of Foam Eductor Do I Need?
Getting a Cost-Effective Foam Setup
Setting up a new foam system and making sure it is cost effective can be difficult. Here’s what to look for in your foam eductor, foam nozzle, and foam attachments.
Eductors easily attach to the 2 ½" discharge of your truck or even between two lengths of hose with 1 ½" or 2 ½" couplings.
For handline operations, you can get a 60, 95, or 125 GPM (Gallons Per Minute) option. 250 and 350 GPM eductors are also available for portable monitor operations.
Foam Compatible Nozzles
You can use a fixed, selectable, or automatic nozzle with your foam operations. It is important to match your nozzle GPM rating to the eductor you are using. This is simple for fixed flow nozzles. With a selectable, you will need to choose the correct GPM setting during use. Automatic nozzles need to include the GPM of your eductor in their flow range to be effective.
We also recommend a lower rated nozzle pressure, usually 75 PSI, because that gives you a lower stream velocity and will result in less stripping away of your bubbles.
You may need a foam attachment or aspirator to help you get the best quality of foam. These attachments entrain air and mechanically agitate the foam solution, giving you a higher quality of finished foam.
Featured Article and Video: How do I Set Up a Cost Effective Foam System?
Is Firefighting Foam Toxic?
Much of the reason for the change from AFFF to Synthetic Fluorine Free Foams (SFFF) is due to the presence of PFOS (perfluorooctane Sulfonate) and PFOA (perfluorooctanoic acid) in the AFFF formulas. These are known as forever chemicals and are linked to various illnesses including:
Diabetes Mellitus Type 2
Kidney Cancer and non-cancerous kidney diseases
Low birth weights
And much more
How Can you Protect your Crew?
Firefighters who work in direct contact with toxic AFFF are at a higher risk of developing illnesses related to exposure. The best way to eliminate future exposure is to end the use of fluorine-based foams and switch to a fluorine-free foam.
Are You Ready for Synthetic Fluorine Free Foams?
The switch away from fluorine-based foams brings up a lot of questions. You may be wondering what challenges you will face during a switch and how to address them. First, let’s explore why AFFF was so popular.
Why was AFFF so Popular?
Compared to earlier types of firefighting foam, AFFF was a significant technological advance in ability to knock down flame and suppress vapor. Plus, it had a longer shelf life, was relatively easy to proportion, had lower application rates, and was more forgiving in application technique. Additionally, AFFF could often be applied using standard fog nozzles without special air aspirating nozzles or foam tubes.
Why is AFFF Being Phased Out?
Toxic chemicals in AFFF are the driving factor behind the phase-out.
From an environmental perspective, PFAS is persistent, bio accumulative, and toxic. This means that the chemicals do not break down and continue to build up in the soil and water.
On the health side of things, firefighter exposure to PFAS and other chemicals in AFFF may have negative health consequences, such as an increased risk of certain types of cancer.
Overall, the firefighting industry agrees that SFFF performance is a downgrade over legacy AFFF performance. The fire service is losing several features and benefits, but this does not mean that SFFF agents are not good firefighting agents. They will just need some adjustments for effective use.
Featured Article: Synthetic Fluorine Free Foams – Are You Ready for the Next Big Change?
What Challenges Will You Face with SFFF?
When it came to legacy AFFF, most manufacturers used a similar formulation that could be counted on to do basically the same thing. Now, SFFF chemical formulations can vary widely by manufacturer. This means you can expect differences when using the products. Here are three main ones you may deal with:
Your new SFFF agent may not be a drop-in replacement for your AFFF agent. The viscosity and chemical properties of the SFFF foam concentrate may or may not be compatible with the foam proportioning device you already use.
We tested ten popular SFFF formulations to understand how well they pick up. You can find the test, results, and a chart of which setting to use with each concentrate right here.
Application Rate Changes:
Foam solution application rates may need to increase when using new SFFF agents. With one major foam agent manufacturer, their AFFF agent needed a 0.15 GPM per square foot application rate. With their new SFFF, a 0.22 GPM per square foot application rate is needed. In some cases, you may need to use a higher GPM eductor to have the same fire suppression capabilities.
Differences in Finished Foam Application:
The primary method of fire suppression at work with an SFFF agent is the foam blanket supplying a barrier between the fuel and atmosphere. AFFF agents not only provided this but included an invisible aqueous film that sped ahead of the finished foam blanket. Because of this, the quality of your foam blanket with SFFF is even more important.
Featured Article: What Will Your Main Challenges Be Using SFFF Firefighting Foams?
Proportioning with New SFFF Formulations
The differences in viscosity and application rate mean some of your equipment may work differently with SFFF formulations. We tested 10 popular foam concentrates to see how well they work with our eductors. Through foam testing, we found that all concentrates worked fairly well with our current eductor line. With the data, we made a few changes and added an additional 3% setting to optimize the pickup of high-viscosity and low-viscosity foam concentrates.
Featured Article: Guide to Eductor Proportioning with New SFFF Formulations
Finished Foam Quality
Finished foam quality is a measure of durability or usefulness of your foam blanket. It is measured in two ways; expansion ratio and 25% drain time. Finished foam quality is a function of the volume of air drawn into the nozzle and the amount of mechanical agitation that occurs in the nozzle or nozzle foam tube.
Why Does Finished Foam Quality Matter?
Specific finished-foam qualities are required to optimize the flame knockdown and fuel vapor securing capabilities of SFFF agents. To apply a high-quality foam blanket, it is important for you to choose nozzles wisely to perfect your SFFF application.
Featured Article: What is the Ideal Finished Foam Quality for Firefighting?
Nozzle Aspirated Foam Systems (NAFS)
One method of foam delivery is a nozzle aspirated foam system. These systems add air to your foam solution at the nozzle device and the mechanical agitation needed to produce finished foam occurs via the nozzle spray pattern entraining air, or via a foam tube attachment.
The parts of a NAFS include a water supply, fire pump, foam proportioner, and a nozzle.
To create finished foam with a NAFS, water is first moved to the eductor inlet by a fire pump. The eductor siphons in, or proportions, a specific amount of foam concentrate into the water. This action creates foam solution. The foam solution is then pumped through the attack hose to the nozzle where air and mechanical agitation take place and finished foam is created.
Featured Article: What is a Nozzle Aspirated Foam System (NAFS)?
Compressed Air Foam System (CAFS)
Another method of foam delivery is a compressed air foam system (CAFS). This method does not require a nozzle. In a typical apparatus configuration, an on-board rotary air compressor is used to discharge compressed air into foam solution inside apparatus piping prior to the point where hose lines or fixed monitors connect to the apparatus.
Extreme mechanical agitation occurs as compressed air and foam solution move through the apparatus piping and/or mixing chamber, through the hose line, and out the nozzle device. This process produces a much smaller foam bubble structure and converts a high percentage of foam solution into finished foam.
Featured Article: How Does a Compressed Air Foam System (CAFS) Work?
Considerations When Choosing a CAFS Nozzle
A nozzle isn’t necessarily needed for a compressed air foam system, but there are advantages to having one. When choosing your nozzle, be sure to consider the following:
Compressed Air Foam Delivery Rates
Operator Skill in Controlling CAFS Pump
CAFS Design and Required Maintenance
Featured Article: 3 Considerations When Choosing a CAFS Nozzle
How do You Evaluate a Nozzle for CAFS?
During your CAFS nozzle evaluation, you will find four criteria that affect firefighter safety and efficiency.
Target Delivery Rate
Before choosing a nozzle, you will need to know your target delivery rate. With CAFS, delivery rates are expressed in gallon per minute of foam solution and cubic feet per minute of compressed air or gpm/cfm.
You should ensure that your chosen nozzle can discharge target delivery rate and provide high-quality foam streams with manageable nozzle reaction force.
You will also want to analyze foam quality and the consistency of your finished-foam product. Some nozzles are too restrictive internally and destroy the compressed air foam bubble structure as the finished-foam media passes through restrictions in the device.
Evaluate stream reach since it affects your stand-off distance from a fire hazard.
Nozzle Reaction Force
Target flow rates discharged through a specific nozzle will have an associated nozzle reaction force. This is nothing new to you and certainly doesn’t go away when using CAFS. You will want to keep your nozzle reaction force manageable so that the nozzle operator can easily maneuver the line.
Featured Article: Evaluating Nozzles for Compressed Air Foam Systems (CAFS)
Firefighting foams are a valuable tool for fire suppression. The switch from AFFF to SFFF will create challenges, but with education and proper evaluations your department can overcome these challenges and experience similar benefits. For some, it may be beneficial to evaluate different foam delivery methods now.