Quantifying the Effectiveness of a Mesh in Mitigating Burning Capabilities of Firebrand Shower

Abstract

The broad aim of this research is to quantify the effectiveness of fences made of metal mesh around buildings in mitigating risks associated with firebrand showers created in wildland fires. This paper aims to (1) quantify the effectiveness of a mesh complying with Australian Standard 3959:2018 against firebrand showers and (2) identify behaviors of firebrands interacting with the mesh. The study was conducted using Red Gum and Cypress Pinewood firebrands inside a wind tunnel at 40 km/h with and without a mesh present for a total of 50 experiments. Two types of effectiveness were defined using the number of holes and their area burnt by the firebrand. The results show the mesh was highly effective against both large and small firebrands except for some long needle shape firebrands. The results are aligned with AS 3959:2018 and show an effectiveness ratio of the mesh in the range 93.2–98.8% for Red Gum and Cypress Pine firebrands at a wind speed of 40 km/h. It was documented that firebrands in interaction with the mesh show one or a combination of eight different mechanisms: passing, stopping, splitting, shattering, pausing, bouncing, slipping and wandering.