A methodology for comparing the relative effectiveness of suppressant enhancers designed for the direct attack of wildfires

- A method for comparing the effectiveness of wildfire suppressants is presented.
- Repeated applications of suppressants on standardised wind tunnel fires are used.
- Performance is determined by the volume used to extinguish flaming combustion.
- Examples presented show that the method has low variability and is highly reliable.
- Normalised results reduce variation in fire spread for comparison across datasets.

Suppressant chemicals are often added to water for use in the direct attack of wildfires to extend the longevity and suppression effects of the water. There are a range of suppressants available, however there has been limited testing to determine which are the most effective. This paper presents an experimental methodology designed to enable the comparison of the relative effectiveness of wildfire suppressants applied in direct attack to fires in forest fuels. The method involves suppressants being applied onto the flaming fronts of standardised laboratory fires burning in uniform forest litter fuels within a wind tunnel through a pressurised system mounted above the burning fuel. The minimum volume of suppressant required to extinguish a standard fire is determined and used to quantify suppressant effectiveness. Examples of the method are presented for plain water and water with three types of wildland fire suppressant. Results show that repeated tests conducted with the same suppressants have low variability (coefficient of variation ~10.8%) and thus high reliability. In order to minimise effects of non-controlled variation in fire behaviour between tests, results can be normalised to produce relative values for comparison across datasets.