Mulching is a common method of fuel treatment. However, it is not currently listed by the U.S. Forest Service as a fuel type in its recommendations for fire retardant coverage levels. FPInnovations researchers set up plots with different coverage levels of retardant on a mulch fuel bed and collected fire behaviour data when a fire interacted with these plots. The results are intended to help wildfire agencies understand the effectiveness of retardant on mulch fuels in developing better suppression plans.
This study focuses on evaluating the relative performance of different commercially available wildland fire chemicals using a custom-built sensible enthalpy rise calorimeter, known as the ‘Thermal Canister.’ Six different fire chemicals were evaluated in this study: Blazetamer 380, AquaGel-K, Firewall II, WD 881C, Thermo-Gel 200 L, and FireIce 561. The evaluation of the relative performance of the fire chemicals was conducted by using the average heat release rate as the primary metric.
It was found that under the test conditions, Thermo-Gel 200L at 3% concentration and FireIce 561 at 1.4% concentration were the most effective at suppressing combustion. The fire chemicals that were least effective at suppressing combustion were Firewall II at 0.25% and 2% concentration and WD 881C at 0.1%, 0.3%, and 1% concentrations. The study also found that certain fire chemicals such as AquaGel-K and FireIce 561 at their highest approved mix ratios were too viscous to be applied and may prove to be challenging to use for firefighting operations.
Data from this study will be used in the Wildfire Chemical Roadmap, where results from multiple tests will help assess the effectiveness and cost of using gels.