Understanding the role of fire retardants on the discontinuous ignition of wildland fuels

This work reports on a theoretical and experimental study on the role of fire retardant treatments on the discontinuous ignition of wildland fuels. The effect of the concentration of fire retardant in the solution applied to the vegetation is as expected to increase the ignition delay time. We found that the fire retardant modifies the fuel bed effective thermophysical properties, delaying the thermal response of the specimen when subjected to an incident heat flux. Nevertheless, the critical heat flux remains unaltered within the experimental error. We followed a proven approach based on the thermal ignition theory and testing which however has not been previously employed to study fire retardants on wildland fuels. To carry this out, we performed experiments on the I-FIT apparatus, which yields repeatable results and controlled boundary conditions. The theoretical model shows a good agreement with the experimental results, delivering simple expressions for pencil-and-paper calculations of the ignition delay time and analytical tools to evaluate effective fuel properties. These results will help CONAF and other forest services around the world to gain insight on the optimal concentrations and delivery methods for these types of products during wildfire response. & COPY; 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

This study investigates the role of fire retardant treatments on the discontinuous ignition of wildland fuels through theoretical and experimental research. The research finds that an increase in the concentration of fire retardant delays the ignition time. The fire retardant modifies the thermophysical properties of the fuel bed, resulting in a delayed thermal response while the critical heat flux remains unchanged. The study provides valuable insights for forest services worldwide on the optimal concentrations and delivery methods of fire retardants during wildfire response. © 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.