Moisture content

n. A measure of the amount of moisture contained in a fuel particle.


  • Discussion


Moisture content of wildland fuel is the mass of water within the particle expressed as a percentage of the particle’s oven-dry mass. Moisture content influences the rate of fuel consumption because the pre-heating and particle burning times are greater at higher fuel moisture levels (Nelson, 2001).  Above a threshold moisture content, which varies according to the type of fuel, combustion is no longer possible because too much of the heat necessary to sustain combustion is being used to drive off the water.  This threshold moisture level is known as moisture of extinction (van Wagtendonk 2006).


  • Units


    Fuel moisture content is most commonly expressed as the mass of water as a fraction or percentage of oven-dry mass. The term moisture fraction is sometimes used when moisture content is expressed as a fraction. Multiply moisture fraction by 100 to get moisture content as a percentage.


  • See Also

  • References

    • Nelson, R.M. Jr.  2001. Water relations of forest fuels.  In: Johnson, E.A.; Miyanishi, K., eds. Forest Fires: Behavior and Ecological Effects. San Diego, CA and London, UK: Academic Press: 79-149.

    • van Wagtendonk, J.W.  2006.  Fire as a physical process.  In: Sugihara, N.G.; van Wagtendonk, J.W.; Shaffer, K.E.; Fites-Kauffman, J.; Thode, A.E., eds. Fire in California’s ecosystems. Berkeley and Los Angeles, CA: University of California Press: 38-57.


  • Notes

    • Author 

      Eric Knapp, Research Ecologist

      Pacific Southwest Research Station