TEST METHODOLOGY FOR COMPARING WILDLAND FIRE CHEMICAL TREATMENTS

摘要

A simple and effective laboratory test methodology was developed for comparing the effectiveness of wildland fire chemicals in delaying the ignition time of vegetative fuels. The proposed test assembly consisted of an electric-powered radiant heater that was used to produce a uniform radiant thermal load, which allowed for a maximum incident heat flux of 90 kW/m~2 to ignite vegetative fuel samples. The samples (untreated, water treated, and foam treated) were mounted on to a load cell, rated at a maximum of 2 kg, to determine the transient mass loss during the combustion process. The time to glowing ignition was determined by visual observation, while the time to flaming ignition was determined by using transient mass loss data. A custom-made heat flux sensor was also used to validate the time to flaming ignition. Statistical t-test analysis was conducted on the time to flaming ignition to determine whether the results were statistically significant for the different chemical treatments. This indicated that the test methodology allowed for effective differentiation between the wildfire chemical treatments by comparing their mean ignition times. The narrow standard deviations of the average ignition times suggested that the test methodology was able to produce repeatable results. In addition to the ignition time, the methodology also provided useful quantitative data such as transient mass loss and heat release all in one test, which can be incorporated into various fire models. The test methodology may also be used to complement the US Forest Service Wildland Fire Chemicals Standard Test Procedures in which no vegetative fuel samples are used, to provide an indication of field performance of wildland fire chemicals.