the time necessary for a wildland fuel particle, under specified conditions, to lose 63 percent of the difference between its current moisture content and its equilibrium moisture content —synonym timelag period —note fuels are grouped into the following classes:

—one-hour timelag fuel fine combustible material consisting of dead herbaceous plants and roundwood less than 0.25-in (0.64-cm) in diameter, including the uppermost litter layer

—10-hour timelag fuel dead fuel consisting of roundwood 0.25- to 1-in (0.64- to 2.54-cm) in diameter and the general layer of litter extending from immediately below the surface to 0.75 in (1.90 cm) below the surface

—100-hour timelag fuel dead combustible material consisting of roundwood 1 to 3 in (2.5 to 7.6 cm) in diameter and the layer of the forest floor that extends generally from 0.75 to 4 in (1.9 to 10.2 cm) below the surface

—1,000-hour timelag fuel dead combustible material consisting of roundwood 3 to 8 in (7.6 to 20.3 cm) in diameter and the layer of the forest floor that extends 4 in (10.2 cm) below the surface This definition last updated 10/01/2008