NWCG Introduction To Wildland Fire Behavior Calculations (S-390) Practice Test

How does wind influence ROS in S-390?

Increased wind generally increases ROS by tilting flames and enhancing heat transfer; applied via WAF Wind decreases ROS by cooling fuels Wind has no effect on ROS Wind only affects smoke production, not ROS

Correct Answer:

Increased wind generally increases ROS by tilting flames and enhancing heat transfer; applied via WAF

Explanation:

Wind drives fire spread by tilting flames toward unburned fuels and boosting heat transfer to those fuels. This heating preheats and dries fuels ahead of the fire, making ignition sooner and the fire advance faster. In S-390, this effect is accounted for with the Wind Adjustment Factor (WAF), which increases the baseline rate of spread to reflect wind conditions. So, stronger wind typically raises the rate of spread, not lowers it or leaves it unchanged, and wind’s main impact is on how quickly the fire moves, not just on smoke.

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