Moisture of extinction [Extinction moisture content]

n. The dead fuel moisture content at which the Rothermel’s (1972) surface fire spread model predicts spread rate will fall to zero.

• Discussion

Moisture of extinction is a parameter of fire behavior fuel models. The use of the term in the Rothermel (1972) surface fire model is misleading because it is not designed to predict extinction; rather, it is included as a way to predict the effect of moisture content on fire behavior (through the moisture damping coefficient). The greater the difference between actual moisture content and the moisture of extinction, the smaller the moisture damping coefficient and therefore the greater the spread rate.

• 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

  • Fire behavior

  • Fire behavior fuel model

  • Moisture content

  • Spread rate

  • Surface fire

   

• References

  • Rothermel, R.C. 1972. A mathematical model for predicting fire spread in wildland fuels. Res. Pap. INT-115. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 42 p.

   

• Notes

  • Author 

    Joe Scott, Research Forester

    Systems for Environmental Management

     

  • Last update 

    August 2007