Training

The Benefits of Container Training

Issue 8 and Volume 9.

Thanks to advancements in building codes, public education and fire prevention technology, the modern fire service responds to fewer structure fires. While this is obviously a positive evolution, one unfortunate consequence is that today’s responders do not get as much field experience with fire as they used to. This means fewer opportunities to build a skillset to combat the many variables that accompany present-day fires.

New Fire Threats

In the days of primarily wood-based construction, flashovers rarely happened. Heavy timber made for good support and cedar shingles allowed for burnout through the roof. Today, construction materials are far more lightweight and synthetic materials are abundant. So while modern advancements have lessened the frequency of fires, modern materials have made the intensity of those fires far greater.

Modern construction designs to save energy limit ventilation points, which in turn supports build-up of super-heated gases. This means that fire will spread rapidly once it starts, producing intense heat and a higher amount of extremely toxic chemicals. If you’ve never seen a flashover, it is striking how fast a small spark can turn a common item like a couch into an intense inferno.

Advances in PPE offer better protection that allows firefighters to go deeper into structure fires, but that extra protection can sometimes give a false sense of security, ultimately leading firefighters into harm’s way. This makes it all the more important that modern firefighters protect themselves with the knowledge that comes from studying the characteristics of fire.

Container Training

For the purpose of training firefighters, the ideal situation would include regular calls for structure fires that all take place in a safe, contained environment conducive to education. This is far from realistic, of course, so departments opt for the next best thing—container training.

Though some may frown on them at first glance, training containers are not just big metal boxes with stacks of burning wood inside. Container systems often have one or more burn areas, referred to as the burn box. A burn box is the 8′ section of the container that holds the burnable fuel loads and is reinforced to withstand extremely high temperatures. More importantly, the design of the burn box helps replicate the conditions of a real structure fire, only on a smaller scale. Typically, plywood or oriented strand board (OSB) is used as the primary fuel, and the walls and the ceiling are lined with it as well. This serves a dual purpose: 1) lining the walls with the material instead of stacking pallets or hay in the middle of a room helps protect the integrity of the structure; and 2) this configuration puts the fuel on all surfaces, which is much closer to reality than a simple stack of wood.

Each burn box is also equipped with a modified barrel that holds what is called the “crib” fire. The crib acts as the seat of the fire, which means it is both the ignition point and the heat source for the entire evolution. In a very real sense, the crib is the engine of any burn session.

Class A (or wood-fueled) containerized training platforms utilize a cumulative, or phased, approach to fire training. Though the preferred fuel is OSB on every surface, Class A systems can utilize other materials such as wood pallets, hay or paper as the primary fuel source for the fire. One of the biggest benefits of Class A fire and smoke is that it behaves the same way it would at a real structure fire, so the training is very true to reality. Specifically, Class A systems provide real flashover experiences for firefighters in a controlled environment. Participants are able to identify and study the traits of a burn that lead to flashover.

Basic Fire Science

Firefighting is a science, and understanding the principles of fire behavior can give responders a significant advantage in conducting a fire attack. What follows is a quick rundown of fire progression—definitely not exhaustive, and worth following up with further instruction inside a container.

Every Class A or structure fire progresses through certain fire stages. With a campfire, for example, a match is the ignition source that ignites some type of kindling, which begins a small incipient stage fire. The incipient stage builds and continues until there is enough heat to begin burning the larger logs. As the fire picks up momentum, it transitions into growth mode. Intensity steadily increases until the campfire plateaus and burns as a fully developed fire. Once the fuel is spent, the flames will begin to die down as the fire decays.

The same stages occur in structure fires, but firefighters aren’t usually on scene to witness this entire progression. In fact, sometimes it is firefighter intervention that alters the environmental variables of a fire in growth mode and induces hazards like a flashover. That is why it is extremely important for firefighters to understand what happens during each stage, and more importantly, how their actions will influence the course of the fire.

Thermal Balance, Off-Gassing & Flashover

During a burn evolution in container training, participants can witness the incipient stage as the crib ignites, begins to build up heat and establishes itself as the seat of the fire. As heat builds, the opportunity arises to discuss a principle called thermal balance.

In nature, everything seeks a thermal balance. If you pick up a cold beverage, your hand gets cold and your drink warms up. When hot metal is submerged in water, the metal cools and water temperature increases. In each case, heat energy is transferred toward a more even balance of temperature. Likewise in a burn box or structure fire, the heat generated by the seat of the fire absorbs into the walls and other fuel as the room temperature and the materials within seek to find a thermal balance. As the fire progresses into growth mode, the fuel (which may not yet be on fire) reaches a point where it can no longer absorb all the heat. At this point, the material will start radiating heat back into the room in the form of superheated gases or smoke. This process is called off-gassing.

Off-gassing is important to understand, because it is what actually makes fire possible. Solids in and of themselves don’t combust; rather, heat can increase a solid’s temperature until it off-gasses, whereupon a chemical reaction between the vapor, oxygen and heat ignites a flame.

Another important element to point out is that the absorption of heat and off-gassing is a continual and cumulative process in a structure fire and in a container training evolution. As the intensity of the fire in the burn box increases, heat is constantly radiating back and forth between the seat of the fire and all surfaces. If not interrupted, this cycle, known as thermal radiation feedback, drives up the temperature and creates an environment full of superheated smoke and/or fire gases.

Flashover occurs when oxygen is introduced to those superheated gasses at an ignition temperature between 1,100 to 1,500 degrees. During container training, instructors will often allow an evolution to progress all the way to a flashover because the environment is controlled, participants are in a safe position to observe the phenomenon and the process provides an invaluable lesson to firefighters. As lessons advance from simple observation of fire behavior, the focus on pre-flashover conditions should shift toward assessing the situation, recognizing the stage of the fire and executing the attack.

The Value for Firefighters

Today’s responders are spending less time fighting real fires, yet modern building materials make fires more dangerous than ever. That means that today’s firefighters need training that teaches them more than just “how to put the cold stuff on the hot stuff.”

Firefighters need the knowledge, confidence and experience that comes from training on realistic fires and learning in conditions they might encounter on a real call. They need training that teaches them the language of fire and smoke behavior. The safe and consistent lessons provided by container training ensure that every participant can witness the conditions that may threaten their life, and develop strategies to help protect them in the line of duty.