Basic concepts of wild land fire latest update with verified solutions

Basic concepts of wild land fire latest update with verified solutions origin The origin is the area where the fire started. It is also the point from which the fire spreads, depending on the fuels present and the effects of wind and slope. When the fire is human-caused, you often find the origin next to a trail, road, or highway, but a lightning strike or campfire can result in a very inaccessible point of origin. Protect the area of origin for subsequent investigation of fire cause whenever possible. head The head is the part of a wild land fire with the greatest forward rate of spread (ROS). Because wind and slope affect the rate and direction of spread, the head is normally either on the edge of a fire opposite to the direction from which the wind is blowing or it is toward the upper part of a slope. The head of a fire often burns intensely and may move with alarming speed. Some large fires may have multiple heads. Ultimately, you have to control the head(s) and prevent the formation of new heads to suppress a wildland fire. fingers Fingers are typically long, narrow strips of fire that extend from the main body of a fire. They form: When a fire burns into mixed fuels; slowing in heavy fuel, but spreading quickly in light fuels Due to variations in terrain or wind direction When the head is split by natural features such as fields, water, or rock outcroppings Caution: Uncontrolled fingers may form new heads. If possible, knock them down when they're small and manageable. pocket A Pocket is the unburned area between the main fire and any fingers. perimeter The perimeter is the outer boundary—or the distance around the outside edge—of the burning or burned area. Also commonly called the fire edge, don't confuse the perimeter with the control line (an inclusive term for all constructed or natural barriers and treated fire edges used to control a fire) or fireline (the part of the control line that is constructed by firefighters). Obviously, the fire's perimeter continues to grow until you get it controlled and extinguished. flanks The flanks are the sides of a wildland fire, roughly parallel to the main direction of fire spread. Flanks are identified as either left or right as you are looking from the heel of a fire toward the head. Control flanks as soon as possible, because: A shift in wind direction may quickly change a flank into a head Fingers often extend from flanks rear The rear, or heel, of a wildland fire is the end opposite the head—that is, relatively closer to the point of origin than to the head. Because fire at the heel usually burns into any prevailing wind, it generally: Burns with low intensity Has a low rate of spread (ROS) Is generally easier to control than the head islands Islands are unburned areas inside the fire perimeter. Because they are unburned potential fuels, patrol them frequently and check for spot fires. Islands close to a control line may flare up later and start spot fires across the control line. You may want to burn islands out, consuming fuels between the perimeter (fire edge) and the control line. spot fires As gases rise from a fire into the convection column, sparks, embers, and burning twigs are carried aloft. Spot fires result as these hot and burning items fall back to the ground or are blown across a fireline by winds. Spot fires can also result when embers or burning fuels roll downhill across the fireline into unburned fuels beyond the main fire. If spot fires burn unchecked, they may form a new head or another major fire. If this happens, firefighters could be trapped between two fires or the fire may move in an unanticipated direction. slopover Also known as breakover, slopover occurs when fire crosses a control line or natural barrier intended to contain the fire. Slopover and spot fires differ mainly in their location relative to the control line: Slopover occurs immediately across and adjacent to the control line Spot fires occur some distance from the control line the green Any area that's not burnt—but is adjacent to an involved area—is called the green. Fuels in the green may be: Live fuels, including: - Vegetation with a high moisture content that is relatively slow to ignite - Vegetation with lower moisture content and highly flammable - Dense, golden-yellow annual grasses and other similar fuels with low moisture content that may burn vigorously Dead fuels—dried vegetation that is highly flammable and will go up like kindling The term green certainly does not define a safe area. It is simply the opposite of the black, or burned, area. The edge of the green is usually where you construct a control line. the black The opposite of the green—the black or the burn—is the area (including both surface and aerial fuels) in which the fire has consumed or "blackened," the fuels. Whether the black is safe or not depends on a few factors. If it is completely burned over and little, if any, unburned fuel remains, the black is a relatively safe area during a fire. However, the black is not always safe. Click the black area to see a few things to keep in mind. You must click on the Warning button before you will be able to proceed. reburns If a surface fire leaves aerial fuels more or less intact in the black, or vice versa, a reburn can occur when burning conditions are more favorable—for example, if the winds shift or humidity drops. This often occurs when fire moving quickly through an area fails to consume all fuels. chain rate of fire spread flaming front part of a fire within which continuous flaming combustion is taking place. Most of the time, the flaming front is the leading edge of the fire perimeter. However, in surface fires, the flaming front may be mainly smoldering combustion. smoldering fire that burns without a flame and is barely spreading A creeping fire burns with a lo creeping fire fire with a low flame and spreads slowly running fire rapid moving fire with well defined head crowning fire burns at top of tree, also known as running and dependent fire torching fire a torching fire periodically ignites the crown of a single or small group of trees or shrubs before returning to the surface. fire whirls are spinning, moving columns of rising air and fire gases that carry smoke, debris, and flames aloft. They're usually formed on the leeward side (protected from wind) of elevated terrain features and can cause spotting. control line refers to all constructed or natural fire barriers. It's also used to describe the treated fire edges used to contain the fire. fire line any cleared strip or portion of a control line where flammable material has been removed by scraping or digging down to mineral soil. anchor point any good place where you can start constructing a fireline. Generally, a fire barrier is a safe anchor point. Using an anchor point minimizes the chance of being outflanked by the fire while the line is being constructed. containment the status of a wildfire suppression action that can reasonably be expected to stop the fire spread under prevailing and predicted conditions. control the point in time when the perimeter spread of a wildland fire has been halted and can reasonably be expected to hold under foreseeable conditions. control a fire Complete the control line around a fire, any spot fire from the fire, and any interior island to be saved Burn out any unburned area adjacent to the fire side of the control lines Cool down all hot spots that are immediate threats to the control line until the lines can reasonably be expected to hold under foreseeable conditions mop-up The mop-up phase marks the final extinguishing of a fire after it has been completely surrounded by control lines. It is a strategy to make a fire safe or to reduce residual smoke. But always be on the ready—blowups and tragedies have occurred in the mop-up stage. fuel Fuel may exist in any of the three states of matter—solid, liquid, and gas. However, only gases burn. The initiation of combustion of a solid or a liquid fuel requires its conversion into a gaseous state by heating. During combustion, heat and chemical changes in the fuel cause fuel gases to evolve from the fuel. So, even though fuel and oxygen are present in the wildland, heat must be added to liberate the fuel gases and initiate the combustion process heat sources Heat sources sufficient to reach ignition temperature may come from: Open flame Sun Lightning Hot surfaces Sparks and arcs Friction Chemical action Electric energy Compression of gases oxygen sources A concentration of approximately 16 percent oxygen is required for combustion, but normal air contains 21 percent—more than enough for combustion to occur. However, some fuel materials contain sufficient oxygen within their makeup to support burning. conduction When two objects of different temperatures contact each other directly or through a medium, heat conducts from the warmer object to the cooler one until their temperatures equalize. Metals such as aluminum, copper, and iron conduct heat readily and can play a significant role in fire spread within structures. However, fibrous materials such as plants and wood are poor conductors of heat. Therefore, heat transfer by conduction has limited effect on the spread of wildland fires. convection gases heated in a fire expand, become lighter, and rise. In a wildland fire, fire gases rise in a convection column, and cooler air flows in to replace the rising gases. In some cases, this inflow is sufficiently strong to affect local winds. As these gases rise up into the column, sparks, embers, and burning twigs are carried aloft. These burning materials fall back to earth up to several miles downwind and can start spot fires well ahead of the main fire. Hot convected gases moving up a slope can dry out fuels lowering their ignition temperature. These fuels also become preheated by the convected heat, thus increasing their susceptibility to ignition and more rapid fire spread. radiation one of the major sources of fire spread in wildland fires. It's as simple as 1, 2, 3: 1—Heat waves, sometimes called infrared rays, radiate in all directions from the heat source. 2—Heat waves travel through air until they are totally or partially absorbed by an opaque object. 3—The opaque object gains heat and in turn radiates heat from its surface. One of the most common examples of radiant heat in a wildland context is fire burning in a narrow canyon. Radiating heat preheats and dehydrates exposed fuels immediately adjacent to the fire and initiates combustion. Another common example is the heat firefighters feel on the fireline—radiant heat is also responsible for many burn injuries to those working near wildland fires. removing oxygen Wildland fires burn in the open air; therefore, attempting to restrict the oxygen supply to a fire (removing oxygen) is usually limited to smothering relatively small fires with dirt. Of course, make sure the dirt you use doesn't have a lot of flammable organic material in it, such as pine needles and dead leaves. removing heat Cooling the fire with water or Class A foam is one of the most common and effective fire extinguishing methods. removing fuel Clearing a space of all surface fuels down to mineral soil (dirt containing little or no organic material) is a common way of controlling and extinguishing wildland fires. This is the basic idea behind the creation of any fireline.