Although fire doesn’t usually move downhill quickly, one serious concern about fires burning down steep slopes is the possibility of burning material rolling downhill , which can ignite fuels below starting another fire.
What factor is the most dangerous in the fire behavior triangle?
Humidity , the amount of water vapor in the air, affects the moisture level of a fuel. At low humidity levels, fuels become dry and, therefore, catch fire more easily and burn more quickly than when humidity levels are high.
Which method of heat transfer is most important to fire behavior on steep slopes?
The steeper the slope, the faster the fire burns. This is because the fuels above the fire are brought into closer contact with the upward moving flames. Convection and radiant heat help the fuel catch fire more easily.
How do slopes affect fire behavior?
3.1 Slope. The slope, or degree of inclination or steepness of an area, can affect the amount of fuel available and can also lead to greater rates of fire spread. The steeper the slope, the greater the preheating of fuels that can occur, and the faster the fire will spread. Fire spreads best uphill.
What slope is most susceptible to fires?
Consequently local winds usually blow up-slope during the day. Because of the local, up-slope winds, wildfires usually burn up-slope. The steeper the slope, the more rapidly the fire will burn up-slope (and more intensely). The reason is because of both greater radiant heat and greater convective heat.
What is the fastest spreading part of a fire?
Head of a Fire: The side of the fire having the fastest rate of spread.
What are 5 critical fire weather conditions?
Summary. The four critical weather elements that produce extreme fire behavior are low relative humidity, strong surface wind, unstable air, and drought .
What are the 3 methods of extinguishing a fire?
All fires can be extinguished by cooling, smothering, starving or by interrupting the combustion process to extinguish the fire. One of the most common methods of extinguishing a fire is by cooling with water.
What are the 4 behaviors of fire?
Fire behavior includes such things as how fast a fire burns (rate of spread), how hot it burns (fire intensity), the presence of fire whirls, and ember production and spotting .
What are the 4 main factors influencing fire spread?
Fire spread depends on the principal methods of heat transfer: conduction, convection, radiation and direct burning .
Does fire travel faster up or down hill?
A fire will burn faster uphill because the flames can reach more unburnt fuel (e.g. trees) in front of the fire. The heat radiating from the fire pre-heats fuel on the slope ahead of the fire, causing the fuel to start burning more quickly.
What increases ROS on a slope?
An easy guide for approximately the ROS due to changes in slope is as follows: ... The first tripling of slope roughly increases the rate of fire spread by a factor of 2 . 2. The second tripling of slope increases the rate of spread by a factor of 4 to 6, depending on fuel conditions.
What are extreme fire behavior characteristics and how would they influence the fire environment?
Extreme implies a level of fire behavior characteristics that ordinarily precludes methods of direct control action. One or more of the following is usually involved: high rate of spread, prolific crowning and/or spotting, presence of fire whirls, strong convection column .
What slope has more shade?
In the northern hemisphere, the north side of slopes is often shaded, while the southern side receives more solar radiation for a given surface area insolation because the slope is tilted toward the sun and isn’t shaded directly by the earth itself.
Which would make the best safety zone?
How do you identify a good safety zone? Consider the distance from the escaped fire as well as topography, winds, fire behavior, and fuels in the area. The best locations are usually in the black , have with a minimum of, or are devoid of, ground/aerial vegetation, or are large bodies of water.
Do fires burn up or down?
All the hot gases in the flame are much hotter (and less dense) than the surrounding air, so they move upward toward lower pressure. This is why fire typically spreads upward , and it’s also why flames are always “pointed” at the top.
