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S-190 Questions and Correct Answers
Wildland/Urban Interface Ans: Line, area, or zone where
structures and other human development meet or intermingle with
undeveloped wildland or vegetative fuels.
Convection Column Ans: Rising column of heated air or gases
above a continuing heat or fire source.
Fire Spread Ans: Since there are 60 minutes in an hour and just
over 60 ft. (18 m) in a chain, using the rule of thumb will give you
a reasonably accurate measurement of the fire's forward progress.
For example:
1 ft. (0.3 m)/minute = 1 chain/hour
10 ft. (3 m)/minute = 10 chains/hour
A fire that burns an area 10 chains by 10 chains is a 10-acre fire.
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Conduction Ans: 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.
Convection Ans: 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 Ans: 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.
Aspect Ans: The aspect of a slope determines the effect of the
sun's heat on the slope's plants and trees, air temperature, and
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moisture retention of the soil. Solar radiant heating can influence
fire behavior by influencing fuel moisture and ignition points. The
southern slopes are more susceptible to fires than northern
slopes.
Slope Ans: -Uphill side of a fire—flames are closer to the fuel
dehydrating, preheating, and igniting them sooner than they would
if they were on level ground
-Wind currents normally move uphill during the day and tend to
push heat and flames toward new fuels
-Upslope fires create a draft, increasing the ROS. 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.
Calculating Slope Ans: The percentage of slope is based on the
ratio of vertical rise to horizontal distance.
To calculate a slope's percentage, follow these steps:
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1. Measure the amount of vertical elevation change then...
2. Divide that number by the horizontal distance and...
3. To change the final number into a percent, multiply by 100.
Saddle Ans: Depression or pass in a ridgeline; low area on a
ridgeline between two higher points.
Chute Ans: A chute is a steep V-shaped drainage
Chimney Ans: Steep, narrow draws or canyons in which heated
air rises rapidly as it would in a flue pipe.
3 Types of Canyons Ans: Box canyons
Narrow canyons
Wide canyons
© 2025 All rights reserved
S-190 Questions and Correct Answers
Wildland/Urban Interface Ans: Line, area, or zone where
structures and other human development meet or intermingle with
undeveloped wildland or vegetative fuels.
Convection Column Ans: Rising column of heated air or gases
above a continuing heat or fire source.
Fire Spread Ans: Since there are 60 minutes in an hour and just
over 60 ft. (18 m) in a chain, using the rule of thumb will give you
a reasonably accurate measurement of the fire's forward progress.
For example:
1 ft. (0.3 m)/minute = 1 chain/hour
10 ft. (3 m)/minute = 10 chains/hour
A fire that burns an area 10 chains by 10 chains is a 10-acre fire.
© 2025 All rights reserved
, 2 | Page
Conduction Ans: 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.
Convection Ans: 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 Ans: 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.
Aspect Ans: The aspect of a slope determines the effect of the
sun's heat on the slope's plants and trees, air temperature, and
© 2025 All rights reserved
, 3 | Page
moisture retention of the soil. Solar radiant heating can influence
fire behavior by influencing fuel moisture and ignition points. The
southern slopes are more susceptible to fires than northern
slopes.
Slope Ans: -Uphill side of a fire—flames are closer to the fuel
dehydrating, preheating, and igniting them sooner than they would
if they were on level ground
-Wind currents normally move uphill during the day and tend to
push heat and flames toward new fuels
-Upslope fires create a draft, increasing the ROS. 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.
Calculating Slope Ans: The percentage of slope is based on the
ratio of vertical rise to horizontal distance.
To calculate a slope's percentage, follow these steps:
© 2025 All rights reserved
, 4 | Page
1. Measure the amount of vertical elevation change then...
2. Divide that number by the horizontal distance and...
3. To change the final number into a percent, multiply by 100.
Saddle Ans: Depression or pass in a ridgeline; low area on a
ridgeline between two higher points.
Chute Ans: A chute is a steep V-shaped drainage
Chimney Ans: Steep, narrow draws or canyons in which heated
air rises rapidly as it would in a flue pipe.
3 Types of Canyons Ans: Box canyons
Narrow canyons
Wide canyons
© 2025 All rights reserved
