What does Bushfire Attack Level (BAL) mean?

Bushfire Attack Levels (BALs) are a way of prescribing a certain standard of building design and construction, to manage potential bushfire risks (by compliance with the Australian Standard AS3959:2018 - Construction of Building in bushfire-prone areas). The BAL system is based on the potential exposure of the site to heat flux exposure thresholds, expressed at KW/m2.
Proximity of the site to hazardous vegetation, surrounding slopes, location of the site and the type of vegetation are used to determine the likely bushfire risk to the site. The Queensland Fire and Rescue Service publication ‘Bushfire Resilient Communities’ provides additional information on bushfire hazard assessments.
Six BALs can be prescribed, including:
- Low - There is insufficient risk to warrant any specific construction requirements but there is still some risk.
- 12.5 - There is a risk of ember attack and construction is expected
- 19 - There is a risk of ember attack and burning debris ignited by windborne embers and a likelihood of exposure to an increased level of radiant heat
- 29 - There is an increased risk of ember attack and burning debris ignited by windborne embers and a likelihood of exposure to an increased level of radiant heat
- 40 - There is a much increased risk of ember attack and burning debris ignited by windborne embers, a likelihood of exposure to a high level of radiant heat and some likelihood of direct exposure to flames from the fire front.
- FZ - There is an extremely high risk of ember attack and burning debris ignited by windborne embers, and a likelihood of exposure to an extreme level of radiant heat and direct exposure to flames from the fire front.


