Part 1A of 6
Bushfire Attack Level Refresher: What BAL Ratings Mean
This Bushfire Attack Level refresher explains what BAL ratings are, why they matter, and how they connect to embers, radiant heat, flame contact and site conditions.
Mark each section as refreshed as you work through the article.
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Learning summary
This short refresher sits between Part 1 and Part 2.
Main goal
You will learn what BAL ratings mean and why they are used in bushfire assessment.
Key idea
BAL describes likely bushfire attack exposure for a building site.
Important note
This is a training refresher only. Always follow current standards, legislation and organisational procedures.
What does BAL mean?
BAL means Bushfire Attack Level.
A Bushfire Attack Level describes the likely level of bushfire attack that may affect a building site.
It is linked to how a bushfire may expose a building to embers, radiant heat and flame contact.
In simple terms, BAL helps connect site conditions with building construction requirements.
However, a BAL is not a guess. It must be determined by using the required method, standards and organisational procedures.
BAL helps answer this question: how much bushfire attack could this building site face?
The BAL rating ladder
The BAL ladder moves from lower exposure to higher exposure.
The BAL rating ladder usually includes BAL-LOW, BAL-12.5, BAL-19, BAL-29, BAL-40 and BAL-FZ.
As the level rises, the likely bushfire attack exposure also rises.
Lowest assessed exposure level.
Primarily ember attack with lower radiant heat exposure.
Moderate exposure, often linked with embers and burning debris.
Higher exposure from embers, debris and radiant heat.
Very high exposure, with stronger heat and possible flame effects.
Flame Zone. This is the highest exposure category.
What changes as BAL increases?
Higher BAL ratings mean higher expected exposure.
As BAL increases, the site may face stronger bushfire attack effects.
First, ember exposure may become more important. Next, radiant heat may increase. Finally, flame contact may become a major concern at the highest levels.
This does not mean every bushfire will behave the same way. Bushfire behaviour can change with fuel, topography and weather.
Therefore, the BAL process must use site evidence, not casual opinion.
Burning material may travel ahead of the fire and collect near vulnerable features.
Heat can affect a building without direct flame contact.
Direct flame exposure is linked with the highest bushfire attack levels.
What affects a BAL rating?
BAL ratings come from site inputs, not guesswork.
Several site inputs affect BAL assessment.
These include the site location, relevant Fire Danger Index or wind speed, vegetation classification, vegetation type and height, distance from vegetation to the building site and slope under vegetation.
Site constraints also matter. For example, unclear boundaries, difficult access or mixed vegetation may affect how information is collected.
Good assessors record these details clearly. As a result, the final BAL can be checked and explained.
Confirm the correct site and building position.
Use the required FDI or wind speed input.
Classify vegetation using the required method.
Measure slope under vegetation where required.
BAL is not just distance
Distance matters, but it is only one part of the assessment.
A common misunderstanding is that BAL is only about how close vegetation is to a building.
Distance is important. However, it must be considered with vegetation type, slope, fire danger inputs and site conditions.
For example, two sites may have a similar distance to vegetation. Yet they may still need different assessment thinking because slope, vegetation or fire danger inputs differ.
Therefore, learners should avoid one-factor thinking. BAL assessment needs the full input chain.
Do not say “the BAL is low” just because vegetation looks far away. Use the required method and all relevant site inputs.
Where this fits in the BAL READY Cycle
This refresher supports the whole six-part series.
The BAL READY Cycle helps learners keep the process in order.
In this part, the main focus is understanding what the final BAL rating means before learning more about bushfire attack, site inputs and reporting.
Know that BAL links to ember, heat and flame exposure.
Use current standards, legislation and procedures.
Use the correct inputs before deciding a BAL.
Record the result and the input chain clearly.
Practical scenario drill
Use this scenario to test your BAL thinking.
Scenario
A proposed building site is near vegetation. The owner says, “The trees are not that close, so the BAL must be low.” You can also see slope under the vegetation and dry fuels nearby.
Question: What is the best response?
Common misunderstandings
These quick corrections help learners avoid poor BAL thinking.
Misunderstanding
BAL is only about distance from trees.
Better understanding
BAL uses several site inputs, including vegetation, distance, slope and fire danger information.
Misunderstanding
BAL removes bushfire risk.
Better understanding
BAL describes exposure and supports construction decisions. It does not remove risk.
Misunderstanding
A BAL can be chosen by looking at the site quickly.
Better understanding
A BAL must be determined using the required method and recorded evidence.
Knowledge check
Answer these quick questions before returning to Part 2.
60-second refresher drill
Use this drill to lock in the main lesson.
- Say what BAL stands for.
- Name the six common BAL levels.
- Explain why BAL is not just distance.
- Name three site inputs that can affect BAL.
- Explain why a BAL must follow standards and procedures.
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