Fire in the Lab

By Samantha Gleissner

Battling wildfires can be a hazardous business. Wildfires are unpredictable and fast spreading; a single change in wind direction or fuel densities can alter the fires nature drastically. The best way to safely battle fires is to be able to understand how they function and even be able to predict the path that the fire may take.  If you are wondering how on earth it is possible to predict the unpredictable, or understand something that is by definition wild?  Fire science is how! Many scientists are now dedicating their work to learning how to understand and predict wildfire movement and alterations with wind changes. By studying fire in the controlled setting of a lab, fire scientists are learning how to more safely manage and defend against wildfires.

In a fire lab you might find mock structures, fabricated forests, and even wind gust chambers! Models are used to perform controlled fire experiments in order to record and analyze fire movement, combustion rates, and even the point at which a burned home or forest is salvageable. Fire Science is an incredibly important field of study that is necessary to give Firefighter every advantage possible when working the fireline.

When battling a fire, firefighters have to consider the path and trajectory of the burn in order to determine whether a fire crew can safely enter an area to battle flames, if a structure is unsalvageable or unstable a firefighter needs to know when it is safe to enter a structure and when it is beyond saving. Combustion rates can determine how quickly and at what temperatures a structure will become consumed. Having a solid understanding of these statistics, backed by scientific research can help in the estimation of periods for safe entry of a structure, or can help fire crews decide when it is best to allow a forest or area to burn out verses putting the effort into putting a wildfire out entirely. In other words, fire research, can literally provide the basis for life and death decisions.

Fire science in the lab isn’t only about the flames; experiments are done to help determine contribution of wildfires to greenhouse gasses, and potential health hazards such as heavy smoke inhalation. Fire science labs can help determine what levels of smoke are dangerous and what levels they are just an irritant. Fire labs determine the amount of carbon monoxide that is dangerous for humans and then use that data to come up with CO detectors that can detect levels of carbon monoxide before they reach lethal levels. Smoke detectors and fire sprinklers have all been products of fire lab experiments, and are just a few lifesaving tools we can be grateful to fire scientists for inventing.

If you enjoy the idea of safely playing with fire in a controlled setting and experimenting with different settings to asses fire dangers to help protect people and homes from those dangers you might want to consider a career in fire science!

Some fire science resources:

http://www.firelab.org/facilities-a-resources/102-smoke-sampling

http://www.firescience.gov

Fire Behavior Triangle Explained

Unlike the Fire Triangle (heat, oxygen, fuel), The Fire Behavior Triangle explains how a fire acts after it is already ignited. The Fire Behavior Triangle is similar in that it is comprised of 3 parts - Weather, Topography, and Fuels – but the complexity of how these components interact on a large scale makes this mnemonic device much more important in the education of wildland firefighters and homeowners alike.

Weather.  The aspects of weather that have the greatest influence on fire behavior are wind, humidity, temperature, and precipitation. Wind has played a vital role in every catastrophic fire in history. It empowers fire by injecting oxygen for combustion and pushing the flames onto unburned fuel. Humidity and precipitation both influence the degree to which fuels are saturated with water, which is important because dry fuels burn easily, while wet fuels are difficult, often impossible, to ignite. Temperature plays a lesser role, but along with low humidity, temperature dries out fuel for a more intense burn.

Topography. Simply put, topography can be described as “the lay of the land”. It may seem odd, but fires don’t burn the same on all landscapes - fires burn much faster uphill because the rising heat from the fire dries out the fuels above it, priming them for easy and rapid combustion. This effect of fire behavior, along with the inaccessibility of mountainous areas to firefighters, makes it significantly harder to fight flames in steep terrains. Fire behavior is also greatly affected by the aspect, or direction the slope faces. Here on the Northern Hemisphere it is the southern-facing slopes that get the most direct sunlight, and therefore are the driest side of any mountain or foothill. Rivers, deserts, and lakes that impede the path of a fire are also included in this category, and are used by firefighters to help contain wildfires.

 Fuels. Anything that can burn in a fire is considered a fuel – grass, trees, piles of leaves, even your home! Areas with a high volume of fuel per acre have the greatest potential to burn intensely in the case of a fire. Dry fuels will burn easier. Fuels that are close together allow fire to spread quickly. In Fire Ecology there are 3 main types of fuels: Ground fuels, surface fuels, and canopy fuels. Ground fuels are combustibles that lie just under the surface, like buried logs or roots, and burn slowly because of the higher moisture and lower oxygen levels. Surface fuels lie on top of or just right above the surface and can include anything from pine needles, leaves, grass, shrubs, or even your back porch. Crown fuels, which typically refer to the crowns, or tops, of trees, are far and away the most dangerous fuel type. If a fire can make its way up to the crown it is significantly harder to suppress, and crown fires can actually spread separately from the ground fire it originated from.

      The Fire Behavior Triangle is a convenient mnemonic device used by fire professionals to quickly and easily teach the fundamentals of fire behavior to just about anyone. Although it’s great for the layman, the Fire Behavior Triangle isn’t exclusively for beginners - it is still taught to wildland firefighters today who need to be constantly aware of the risky, unpredictable nature of fire behavior. Fire behavior is complicated and hard to predict even for experts, but when broken down into its 3 most basic components it is possible to understand, on a very basic level, how fires act in different ecosystems, seasons, weather, or terrains.