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Unit 5: Fuel Moisture

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Natural Fuels   ::   Environmental Factors   ::   Timelag   ::  Dead Fuels  ::   Ignition & Combustion   ::   Exercises

Determining Dead Fuel Moisture Content

We have covered natural fuel complexes and their ranges of fuel moistures, environmental factors affecting fuel moisture, and the fuels time lag concept. We're now ready to discuss methods of determining dead fuel moistures and lead you through the steps to making your own calculations.

Determining Fuel Moisture Contents for Each of the Timelag Categories

Fuel moisture contents can be determined for each of the timelag categories by these means:

  1. 1-hour timelag fuels.
    1. Fuel moisture charts
    2. National Fire Danger Rating System nomograms
    3. Drying oven and scales
  2. 10-hour timelag fuels.
    1. Fuel moisture sticks.
    2. NFDR or National Fire Danger Rating System nomograms
    3. Drying oven and scales
  3. 100-hour timelag fuels.
    1. NFDR System nomograms
  4. 1000-hour timelag fuels.
    1. NFDR System nomograms

Determining fuel moisture percents for 100-hour and 1,000-hour time lag fuels gives managers an indication of drought conditions and overall severity of a fire season. 10-hour fuels are much more important in making fire behavior predictions than 100-hour fuels, but not nearly as important as 1-hour fuels. One-hour fuels are the primary carrier of the fire. We will therefore work primarily with 1-hour time lag fuels in this course.

How the tables are to be used : First of all, you will determine a reference fuel moisture for day or night by entering dry bulb temperature and relative humidity into a table. Next, you will determine a fuel moisture correction value from the tables by considering the month, time of day, aspect, and fuel exposure to sun or shade. The correction value is then added to the reference fuel moisture to get the adjusted dead fuel moisture.

Using Dead Fuel Moisture Tables

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Copyright 2008, by the Contributing Authors. Cite/attribute Resource . admin. (2005, November 07). Unit 5: Fuel Moisture. Retrieved January 07, 2011, from Free Online Course Materials — USU OpenCourseWare Web site: http://ocw.usu.edu/Forest__Range__and_Wildlife_Sciences/Wildland_Fire_Management_and_Planning/Unit_5__Fuel_Moisture_6.html. This work is licensed under a Creative Commons License Creative Commons License