Online Exclusive

Basic Foam Operations - Part 1

Today’s firefighters are trained in a host of topics and the amount of information that they are exposed to can become quite overwhelming. Nevertheless, it is the responsibility of all members to immerse themselves into the job and learn everything they can. In this day of limited staffing, it is imperative that each member of the team be able to contribute the most to their company, from the newest rookie firefighter to the seasoned company officer. There is no room to hide in today’s fire service.

Responding to incidents involving Class B spills and fires are no exception. Our members must have a working knowledge of what to do upon arrival. Theory and practice will keep our companies and personnel safe.

The Need for Effective Foam Operations

One of the topics that all members should have a solid working knowledge of is in basic foam operations. Not only does the proper delivery of finished foam extinguish a flammable or combustible liquid, it can also be used to prevent fires from even happening.

The need for fire departments to respond to incidents involving flammable and combustible liquids is certainly not new. You could go back in time a century before and find that even the Ford Model T had a 10-gallon fuel tank and versions were available that ran on gasoline (a hydrocarbon fuel) and ethanol (a polar solvent). Take a look at the history of the automobile on the Web and you can get an idea of just how our present infrastructure and transport system started.

Now, take into account the need for an infrastructure that supports the ever-growing vehicle industry and what you have are communities that need municipal fire departments capable of handling such incidents. As time goes on, this need will continue to magnify. Today, we have commercial vehicles on the road that typically have 80- to 100-gallon fuel tanks, and SUV’s and pickup trucks that have fuel tanks with more than 40 gallons of fuel. The need for an effective response to incidents involving flammable and combustible liquids is significant.

This series of articles is designed to build upon the training each member has received thus far in basic foam operations for Class B type incidents. It is a very basic approach that is designed to give our company firefighters and fire officers a more thorough grasp of what could be a very in-depth topic. Also, the topic of Class A foam is another interesting avenue of study, but it is outside the realm of this series; please take a look at the exceptional references and sources at the end of this article for further study. The primary topics that we’ll cover over the next seven articles include:

  • Class B fires and spills
  • Types of foam concentrate
  • How foam works
  • Proportioning
  • Application rates
  • Applying foam
  • Typical scenarios
  • Setting up a foam delivery system in your department

In the fire service, we can be called upon to respond to a variety of incidents. Fires and spills involving flammable or combustible liquids shouldn’t be a surprise. With minimal basic equipment and through training, familiarization and study, every engine company should be able to execute a basic foam operation. Together, the multiple units that make up a first-alarm assignment should be able to engage in moderately sized operations. It is this basic approach to spill and fire response that will guide us over the next few articles and set the stage for even larger scale operations.

As for overall training and experience of each company member, well, that can vary dramatically. All of our probationary firefighters have received a healthy background into the five classifications of fire. During basic training, there was an emphasis of how to extinguish each of these classes and the advantages and disadvantages of the different types of extinguishing agents. As our more seasoned firefighters have continued with their training, they have developed a greater respect and additional real-world experiences that build upon what they were taught years before. The company officer, who has the responsibility of commanding the company in battle has (hopefully!) continued with their training and can safely lead their troops into any of a myriad of situations and not get them hurt. Nowhere could a situation go from boring and mundane to explosive in the blink of an eye than when dealing with ignitable vapors and gases. Let’s take a look at the typical Class B incidents that we might encounter at any time.

Class B Fires and Spills

As a review, we’ll go over Class B fires. Simply put, Class B fires are flammable and combustible liquids and gases. The difference between a flammable and a combustible liquid is the temperature at which vapors are given off. Combustible liquids have a flashpoint above 100 degrees Fahrenheit, while flammable liquids give off ignitable vapors (have a flashpoint) below 100 degrees Fahrenheit.

For example, gasoline is a flammable liquid and gives off flammable vapors well below 100 degrees Fahrenheit. Some common sources, such as the International Fire Service Training Association’s (IFSTA) Principles of Firefighting Foam, 2nd Edition, use a flashpoint of -45 degrees Fahrenheit. For different blends of gasoline, check out the various sources available. The specific characteristics can differ from source to source.

Diesel fuel is a combustible fuel and gives off ignitable vapors over 100 degrees Fahrenheit. Sources such as IFSTA’s Principles of Firefighting Foam, 2nd Edition, use 126 degrees as the flashpoint. As an interesting side note, during the writing of this series my research found various credible Web-based sources and several Material Safety Data Sheets (MSDS) that identified the flashpoint of diesel fuel from 100 degrees to over 160 degrees.

Based on the facts for gasoline and diesel fuel, we could never cool gasoline to the point where we could prohibit vapors from being released. Only in the most extreme settings on the planet could the temperature be so cold that gasoline stops giving off vapors. A combustible liquid, on the other hand, can be cooled (such as through environmental conditions like a very cold winter day) to be rendered relatively safe. Nevertheless, there is always the potential for danger and any fuel spill should be given a wide berth. While we can minimize the danger, either through knowledge or actions, there is always a danger when dealing with any type of Class B fuel incident.

The different types of Class B fuels are numerous to say the least. Class B fuels can include everything from propane, natural gas, gasoline, paint, oils, lacquers, paint thinners, ethanol, kerosene, alcohol, and countless other types of liquids and gases. The potential threat to the fire service is varied and numerous. This fact alone should translate into more training time because there are so many dangers out there that can harm us!

The lower the temperature at which the fuel gives off vapors, the greater the potential for ignition. In addition, on a hot summer day for example, fuels are even more volatile and more likely to give off ignitable vapors. This is another size-up factor that has to be considered as part of the response.

One interesting point about Class B fires is that it includes both liquids and gases. Thus a propane leak has the potential to become a Class B fire. But, because of its gaseous properties and its three-dimensional expansion after being released from its vessel, propane would not be fought with foam. Foam application would be ineffective in such a situation.

For fires involving similar types of fuels, whereby the fuel converts to a gas immediately upon escape from the pressurized vessel (such as liquid propane), it is best to extinguish such a fire, or prevent ignition, by shutting off the supply. The same principle applies for any fire or leak involving other types of gases, such as a leak of natural gas. Foam is not the tool of choice; shutting off the fuel supply from a safe location is the tactic of choice. Furthermore, fires that involve a third dimension, such as a fuel being discharged under pressure and cascading downward or spraying outward, is very difficult to extinguish using a typical foam stream. Again, knowing the importance of fuel shutoffs can be of enormous value towards the mitigation of the incident. Take for example, the fuel shutoffs that you might see at the local gas station. Fuel spewing out under pressure may be easily controlled through pre-incident knowledge of such a shutoff. Not all of our incidents have to be front-page headlines. In many cases, a serious incident can be prevented through simple techniques.

In this series of articles, we’ll confine our studies to flammable and combustible spills and the ensuing fires that could develop. Also, we’ll concentrate on incidents involving spills. For our purposes, we’ll use the parameters from NFPA 11: Standard for Low-, Medium-, and High-Expansion Foam, 2010 Edition as it relates to spills of less than one inch in depth. Such incidents are more common to the first responder. The topics of incidents involving large industrial complexes, tanks, and infrastructure are covered in great depth in NFPA 11 and these topics are well outside the scope of this article series. For the typical spill that we may be called to, foam application can be of great value. Knowing the basics and being able to rapidly establish an effective foam stream can mitigate a potential disaster from even happening. Again, the key is training and understanding before the incident!

Foam is an effective tool in our toolbox. But if it is used improperly, all of our time and resources spent could be completely wasted. This is because not only is there the category of Class B liquids and gases to understand, but there are also different types of liquids that are not compatible with all types of foam.

Hydrocarbon fuels are typical of the responses we encounter on a day-to-day basis. It includes flammable liquids such as fuel oils and diesel fuel, kerosene, and gasoline (although newer blends of gasoline may be problematic and we’ll discuss that later). These fuels shed water and have a specific gravity of less than one, which means they will float on top of water. Hydrocarbons do not dissolve in water.

All members of the company must have an academic understanding of the theory as well. The truly valuable firefighter is the member that has both practical experience as well as an academic understanding. Knowing that the specific gravity of gasoline allows it to float on top of water allows a firefighter to take the necessary action to mitigate the threat.

Other types of fuels are referred to as polar solvents and these mix readily with water. Examples of polar solvents include flammable liquids such as alcohol, acetone, and even paint thinner. Both polar solvents and hydrocarbons can be a problem if we don’t know what we’re getting in to. The ability of a polar solvent to mix with water can be problematic. The danger of fire is still present up to a certain point. Beyond this point there is the potential to dilute the fuel to such an extent that it is incapable of burning, but other serious conditions could arise such as environmental damage or other types of unexpected contamination.

A key to our success is knowing the advantages and disadvantages of our equipment and abilities, and the hazards to which we are responding. A key disadvantage in the use of foam is that foam is not a cure-all for all types of incidents. Since foam is primarily water, it means that you cannot use it on an energized electrical source (a Class C fire) because of the danger of electrocution. Foams used on a Class D fires (combustible metals) can be another potential disaster. With foam being anywhere from 94 to 99 percent water, its application on energized electrical equipment and burning metals is unsafe.

Also, there are specialized types of foams that are geared towards hazardous materials incidents of a more technical nature. These foams concentrate on creating a seal over top of the chemical to prevent the release of vapors. See the different manufacturers in the endnotes for further details. There are a variety of specialty foams that are worth reading about and it is certainly an interesting topic, but it is also outside the scope of this series.

In addition, there are the advantages of Class A foam. Class A foam, like its name implies, is used on fires involving Class A combustibles and is not compatible with attacking a flammable liquids fire. This is another valuable tool in the toolbox. The surface tension of water is changed and this allows bailed materials such as bundled newspapers, for example, to be penetrated more effectively than plain water alone. This effective tool supplements traditional firefighting tactics, but doesn’t replace the need for the basics, such as the need for safe and effective overhaul tactics.

Even some types of Class B foams, such as Aqueous Film Forming Foam (AFFF), can be used to penetrate Class A combustibles. The principle of changing the surface tension with the various surfactants that are part of the foam concentrate allows for a reduction in overhaul time. This is not a primary use of Class B foams, but it goes to show that foam concentrates have great value.

As for the extinguishment aspect, the firefighter knows that for a fire to go out, they have to remove one side of the fire tetrahedron. This simply translates into one of the four methods below:

  • Cooling of the fuel. Most often this is done with water. For flammable liquids that generate vapors at very low temperatures, this is highly impractical and potentially unsafe. Foam does offer a cooling ability and can assist in cooling nearby metals that were previously exposed to fire.
  • Inhibiting the chemical chain reaction. The use of specialized extinguishing agents can effect extinguishment, but this is geared toward more localized and limited spills that have ignited.
  • Removal of the fuel. This could be as simple as shutting off the flowing fuel source, such as using the emergency shutoff that is strategically placed near a fuel pump.
  • Eliminating the oxygen. This is a key feature of the extinguishing properties of foam. The ability to float a layer of foam on top of a fuel spill simply creates a barrier between the fuel and the oxygen; it excludes the fuel vapors from mixing with oxygen. The ignitable vapors are smothered, suppressed, and prevented from mixing with oxygen.

There are a variety of extinguishing agents out there that can be used on a flammable liquid fire. Carbon dioxide and dry chemical agents are just two examples. While these agents are effective, they do have their limitations. For example, both can knock down a fire by either excluding oxygen (carbon dioxide) or inhibiting the chemical chain reaction (dry chemical), but neither can prevent re-ignition. Foam offers us many advantages, but it is incumbent on the firefighter to know these.


Let’s review what we have covered. Firefighters should have a solid grasp of all classifications of fire. Knowing the four means of extinguishing a fire leads to efficiency, effectiveness, and safety on the fireground. Each classification of fire presents a hazard and each extinguishing agent has its advantages and disadvantages. Knowing how to use each extinguishing agent is critical.

We can now see that Class B fires are a bit more complex than what we might have previously envisioned. Knowing if a liquid is a flammable or a combustible liquid can help to orient our size-up. Furthermore, conditions can also affect our size-up. For example, a combustible liquid spill onto a blacktopped street on a cold February night would be less prone to giving off ignitable vapors than that same spill on a 105 degree sunny July afternoon. Such a condition would be more likely to heat up a fuel that normally would have been more stable. Again, knowing the basics of fire behavior and chemistry can gear your size-up in the right direction!

In addition, the firefighter has to understand that fuels are not all alike. Some can mix with water and some will shed water. As we start to discuss the basics of foam attack procedures, we’ll see that not all foams are created equal. To apply the wrong foam to a spill or fire can result in greater danger or at the very least, a waste of foam resources.


  • Principles of Foam Fire Fighting 2nd Edition is available through the International Fire Service Training Association (IFSTA).  This text is an exceptional resource on the entire foam process including Class A and B foams.  This textbook and many other related topics can be found at their web site at:
  • NFPA 11: Standard for Low-, Medium-, and High-Expansion Foam (2010 edition) has exceptional details regarding foam application for a host of incidents and can be purchased via the NFPA's website at:
  • While not related to this series of articles, the author Dominic Colletti is one of the nation's foremost authorities on the topic of Class A foam.  He has authored extensively on the topic and a downloadable report that he authored on Class A Foam for structural firefighting can be found at:
  • Kidde Fire Fighting - National Foam web site has additional details of different types of foam concentrates and other products.  It offers very specific details to the firefighter and fire officer.  The web link is:,8061,pageId%3D3513%26siteId%3D465,00.html
  • Chemguard Fire Suppression Solutions offers information on many foam concentrates and other products. The link for this site is:
  • Ansul's Firefighting Foam Products offers additional details like the web links above.  It is another great source of data and can be found:
  • Task Force Tips Nozzles is a major producer of nozzles and appliances.  Their web site has many downloads that are available on foam proportioning and other products.  The web link can be found here:
  • Akron Brass Company is also a major producer of nozzles and appliances.  Their web site offers details on foam proportioning systems and other resources.  The link for them is:

ARMAND F. GUZZI JR. has been a member of the fire service since 1987.  He is a career fire lieutenant with the City of Long Branch, NJ, Fire Department and is the deputy director of the Monmouth County, NJ, Fire Academy where he has taught for over 20 years.  He has a masters degree in management and undergraduate degrees in fire science, education, and business administration. View all of Armand's articles here. He can be reached via e-mail at or