S-190 Intro to Wildland Fire Behavior Questions and Answers
Latest Update Graded A+ - 69 Questions and Answers Already
Graded A+ Premium Exam Tested And Verified
Subject Area Wildland Fire Behavior
Description This exam covers advanced concepts in wildland fire behavior including the fire
triangle, fuel moisture dynamics, fire spread modeling, crown fire development,
spotting, fire whirls, topographic influences, and safety zones. It is designed to
test deep conceptual understanding and application of principles from the S-190
course.
Expected Grade A+
Total Questions 69
Duration 3 hours
Learning Outcomes 1. Analyze the interaction of weather, fuels, and topography in determining fire
behavior.
2. Predict fire behavior changes under varying environmental conditions.
3. Apply safety zone guidelines and fireline strategies based on fire behavior
predictions.
4. Interpret fire danger rating system components for operational decisions.
Accreditation Meets National Wildfire Coordinating Group (NWCG) standards for S-190
certified training at U.S. university level.
Page 1
,1. A wildland fire is burning on a 60% slope with fuel and weather identical to
flat ground. Which factor best explains the increased rate of spread uphill?
Answer: Radiant and convective heat from the fire preheat the upslope fuels.
On steep slopes, flames are closer to the unburned fuels above, allowing more
efficient preheating by radiation and convection. This preheating dries and
ignites fuels faster, increasing spread rate. Aspect does not inherently vary with
slope steepness, wind is not necessarily higher, and gravity's effect on flames is
minor compared to heat transfer.
2. Given a temperature drop from 95°F to 75°F and relative humidity increase
from 10% to 40%, the dead fine fuel moisture (from laboratory equilibrium) is
most likely to:
Answer: Triple
At 95°F and 10% RH, equilibrium moisture content is approximately 2-3%. At
75°F and 40% RH, it is approximately 7-8%. This represents an increase by a
factor of about three, not just doubling or halving.
3. A surface fire has a flame length of 5 ft. The canopy base height of the
overstory is 12 ft, with continuous ladder fuels. Which statement best describes
the expected fire behavior?
Answer: Passive crown fire may occur.
According to Van Wagner's crown fire initiation model, when flame length
exceeds one-third of the canopy base height, passive crown fire is possible. Here,
5 ft > 4 ft (1/3 of 12 ft), so passive torching may occur, but not active crown fire
because flame length does not exceed the full canopy base height.
4. Spotting is most likely to occur when:
Answer: Wind speed exceeds the critical threshold for firebrand lofting.
Spotting requires firebrands to be lofted and carried by wind. If wind speed is
below the threshold needed to lift and transport firebrands, spotting distances are
minimal. The other options describe conditions that generally reduce fire activity,
making spotting less likely.
Page 2
, 5. Which topographic condition is most likely to generate a fire whirl?
Answer: Lee side of a ridge
Fire whirls often form in the lee of ridges where wind eddies and turbulence are
created. This rotating region can stretch and intensify vorticity, drawing in hot
gases and flames. Flat areas and valley floors lack the necessary wind shear, and
ridge tops experience more uniform flow.
6. If air temperature decreases from 90°F to 70°F while the dew point remains
constant at 55°F, what is the approximate percent change in relative humidity?
Answer: Increase by 100%
At 90°F and 55°F dew point, RH is about 30%. At 70°F and same dew point, RH
is about 60%. This is a 100% increase (doubling) in relative humidity. The
decrease in temperature with constant moisture content always raises RH.
7. In the Northern Hemisphere during summer afternoons, which slope aspect
tends to have the highest fuel moisture content?
Answer: North
North-facing slopes receive the least direct solar radiation in the Northern
Hemisphere, resulting in lower temperatures and higher fuel moisture.
South-facing slopes receive the most sun, drying fuels. East and west aspects are
intermediate.
8. At 0600 hours, a fire is burning on a west-facing slope with no synoptic
winds. What is the most likely local wind direction?
Answer: Downslope
During the night and early morning, slopes cool, causing air to sink and create
downslope (katabatic) winds. Upslope winds develop after sunrise when heating
begins. At 0600, near sunrise, downslope winds still dominate until thermal
reversal occurs.
Page 3
Latest Update Graded A+ - 69 Questions and Answers Already
Graded A+ Premium Exam Tested And Verified
Subject Area Wildland Fire Behavior
Description This exam covers advanced concepts in wildland fire behavior including the fire
triangle, fuel moisture dynamics, fire spread modeling, crown fire development,
spotting, fire whirls, topographic influences, and safety zones. It is designed to
test deep conceptual understanding and application of principles from the S-190
course.
Expected Grade A+
Total Questions 69
Duration 3 hours
Learning Outcomes 1. Analyze the interaction of weather, fuels, and topography in determining fire
behavior.
2. Predict fire behavior changes under varying environmental conditions.
3. Apply safety zone guidelines and fireline strategies based on fire behavior
predictions.
4. Interpret fire danger rating system components for operational decisions.
Accreditation Meets National Wildfire Coordinating Group (NWCG) standards for S-190
certified training at U.S. university level.
Page 1
,1. A wildland fire is burning on a 60% slope with fuel and weather identical to
flat ground. Which factor best explains the increased rate of spread uphill?
Answer: Radiant and convective heat from the fire preheat the upslope fuels.
On steep slopes, flames are closer to the unburned fuels above, allowing more
efficient preheating by radiation and convection. This preheating dries and
ignites fuels faster, increasing spread rate. Aspect does not inherently vary with
slope steepness, wind is not necessarily higher, and gravity's effect on flames is
minor compared to heat transfer.
2. Given a temperature drop from 95°F to 75°F and relative humidity increase
from 10% to 40%, the dead fine fuel moisture (from laboratory equilibrium) is
most likely to:
Answer: Triple
At 95°F and 10% RH, equilibrium moisture content is approximately 2-3%. At
75°F and 40% RH, it is approximately 7-8%. This represents an increase by a
factor of about three, not just doubling or halving.
3. A surface fire has a flame length of 5 ft. The canopy base height of the
overstory is 12 ft, with continuous ladder fuels. Which statement best describes
the expected fire behavior?
Answer: Passive crown fire may occur.
According to Van Wagner's crown fire initiation model, when flame length
exceeds one-third of the canopy base height, passive crown fire is possible. Here,
5 ft > 4 ft (1/3 of 12 ft), so passive torching may occur, but not active crown fire
because flame length does not exceed the full canopy base height.
4. Spotting is most likely to occur when:
Answer: Wind speed exceeds the critical threshold for firebrand lofting.
Spotting requires firebrands to be lofted and carried by wind. If wind speed is
below the threshold needed to lift and transport firebrands, spotting distances are
minimal. The other options describe conditions that generally reduce fire activity,
making spotting less likely.
Page 2
, 5. Which topographic condition is most likely to generate a fire whirl?
Answer: Lee side of a ridge
Fire whirls often form in the lee of ridges where wind eddies and turbulence are
created. This rotating region can stretch and intensify vorticity, drawing in hot
gases and flames. Flat areas and valley floors lack the necessary wind shear, and
ridge tops experience more uniform flow.
6. If air temperature decreases from 90°F to 70°F while the dew point remains
constant at 55°F, what is the approximate percent change in relative humidity?
Answer: Increase by 100%
At 90°F and 55°F dew point, RH is about 30%. At 70°F and same dew point, RH
is about 60%. This is a 100% increase (doubling) in relative humidity. The
decrease in temperature with constant moisture content always raises RH.
7. In the Northern Hemisphere during summer afternoons, which slope aspect
tends to have the highest fuel moisture content?
Answer: North
North-facing slopes receive the least direct solar radiation in the Northern
Hemisphere, resulting in lower temperatures and higher fuel moisture.
South-facing slopes receive the most sun, drying fuels. East and west aspects are
intermediate.
8. At 0600 hours, a fire is burning on a west-facing slope with no synoptic
winds. What is the most likely local wind direction?
Answer: Downslope
During the night and early morning, slopes cool, causing air to sink and create
downslope (katabatic) winds. Upslope winds develop after sunrise when heating
begins. At 0600, near sunrise, downslope winds still dominate until thermal
reversal occurs.
Page 3
