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Calcimator

Prescribed Burn Planning

Estimate fire behavior for prescribed burns including rate of spread, flame length, and intensity based on fuel, wind, slope, and moisture conditions.

Inputs

tons/acre
mph
%
%

Results

Fire Behavior Classification

Low — Hand tools effective

Estimated Flame Length

1.3 ft

≈ 5 credit cards

Condition AssessmentWithin prescription — conditions favorable
Rate of Spread0.1 chains/hr
Rate of Spread0.1 ft/min
Fireline Intensity10 BTU/ft/s
Fuel Consumed1%
PM2.5 Emissions0 tons/acre
Heat Per Area8,712
Heat Per (sq ft)100
How to Use This Calculator
  1. Enter the Fuel Load in tons/acre and the Wind Speed (mid-flame height) in mph.
  2. Enter the Slope percentage and Fine Fuel Moisture percentage for current conditions.
  3. Review the Fire Behavior Classification and Condition Assessment to decide if conditions are within prescription.
  4. Check Flame Length and Rate of Spread in chains/hour to verify fireline intensity is controllable.
  5. Use PM2.5 Emissions and Fuel Consumed percentage for smoke management planning.

What each input means

Fuel Load
Dry fuel weight on the ground in tons per acre. Light fuels: 1-3, moderate: 3-8, heavy: 8+.
Wind Speed (midflame)
Midflame wind speed in mph. Typically 1/3 to 1/2 of 20-ft wind speed in timber.
Slope
Terrain slope as percentage. Fire spreads faster uphill. 0% is flat, 100% is 45 degrees.
Fine Fuel Moisture
Moisture content of dead fine fuels (1-hour fuels). Ideal for Rx burn: 8-20%. Below 5% is dangerous.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Fuel Load = 5, Wind Speed (midflame) = 5, Slope = 10, Fine Fuel Moisture = 12 = 4 input(s) provided
  2. Calculate Fire Behavior Classification
    Low — Hand tools effective = Low — Hand tools effective
  3. Calculate Estimated Flame Length
    Estimated Flame Length
    1.3 = 1.3
  4. Calculate Condition Assessment
    Within prescription — conditions favorable = Within prescription — conditions favorable
  5. Calculate Rate of Spread
    Rate of Spread
    0.1 = 0.1

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