Mass Flux During the Piloted Ignition of Moist Layered Leaf Fuels Under External Radiant Heat Flux

ABSTRACT This study investigated mass flux patterns of layered moist leaf samples to illustrate the wide measurable response across a representative set of vegetation types. A series of experiments with 24 plant species was conducted using a cone calorimeter. The samples' moisture content (FMC) varied between 3.2% and 78.6%, and the radiant heat flux was set at 35, 55, 70, and 85 kW m −2 . The initial mass loss of the samples exhibited quasilinear trend, allowing for the extraction of pre‐ignition mass flux , which represents the combined release of moisture and pyrolysis products. Under the same radiation heat flux, was essentially identical for the samples with the same properties but varying mass loading, consistent with the observed ignition modes and times. Measurements indicated that fluctuates widely in a vast range between 3.7 and 21.5 g m −2 s −1 for the samples undergoing smoldering and in the presence of a flame; no systematic linkage between ignition mode and the measured was observed. As rises, ignition time shortens and peak HRR increases, mirroring the field‐observed cessation of fire spread when FMC exceeds ~40%. Live leaves exhibited an additional mass loss flux that lengthened ignition time by one order of magnitude, especially for high FMCs. While data for FMC > 40% provide a quantitative moisture target for green barrier irrigation and prescribed burning buffer zones, the identified variation patterns among FMC, and may supply input bounds for future fire spread model parameterization.