Why would a practitioner use S-390 calculations during suppression activities?

• A. To forecast rainfall during the season.
• B. To anticipate fire behavior, plan line construction, and ensure safety of personnel and resources.
• C. To determine the salary of crew members.
• D. To schedule maintenance for equipment.

Answer: (B)

S-390 calculations help you translate weather, fuels, and topography into a forecast of how a fire will move, which is essential during suppression. By estimating factors like rate of spread, flame length, and spotting potential, you gain a clear sense of where the fire is likely to threaten your line and crew positions. That foresight guides tactical decisions: where to construct or reinforce a control line, how to position crews and equipment for the safest and most effective defense, and when to implement contingency plans or backfires. In short, these calculations turn what you observe on the ground into actionable, safety-focused suppression actions.

They aren’t used for predicting rainfall, setting salaries, or scheduling maintenance. Those areas rely on meteorology for weather forecasts, human resources, and logistics/maintenance systems, not fire behavior calculations.