Step 1: Determine Reference Fuel Moisture (RFM)
Day Time Hours 0800 – 1959 (Table A)
Night Time Hours 2000 – 0759 (Table B)
- Dry bulb Temperature is determined for the time period in question either by measurement or forecast.
- Using the intersection of dry bulb temperature (F) and Relative Humidity (%) determine reference Fuel Moisture (RFM) in percent.
Step 2: Using the Dead Fuel Moisture Content Corrections, match the table having Spring/Fall months (Table C), summer months (Table B) or Winter months (Table D) with the appropriate month.
- Determine if your Fine Dead Fuels are shaded (> 50% shading of surface fuels) or exposed (<50 shading of surface fuels). Shading can be due to cloud cover and/or canopy cover.
- Determine the aspect of the point (area) for which you are calculating Probability of Ignition (PI).
- Determine the slope: (0-30%) or (>30%).
- Calculate the Dead Fuel Moisture Content Correction for each aspect, slope, appropriate time of day, and the elevation differences between the location of the projection point and the RH/Temp site location
- A – 1000 feet – 2000 feet above site
- L – 1000” of site location
- B – 1000 feet to 2000 feet below site
Step 3: Determine Fine Dead Fuel Moisture by adding the Reference Fuel Moisture (step 1) with the Fuel Moisture Correction (step 2).
Step 4: To determine Probability of Ignition:
- Use the Fine Dead Fuel Moisture (Step 4), shading present (Step 2a), and the dry bulb temperature (step 1b)
- Using the Probability of Ignition Table to determine your PI.
Step 5: Nighttime Calculations
- Use Table E for Reference Fuel Moisture
- Use Table F for Dead Fuel Moisture Content Corrections
- Use Probability of Ignition Table as in Step 4.