More about the Bushfire Attack Levels

WA BAL Report are experts at BAL Assessments and BAL Reports. The purpose of a BAL Assessment Report is to calculate the BAL Rating of a property. The BAL Rating is used to determine the construction measures that are required to be implemented to ensure that the property is as well protected from bushfire attack as possible.

There are 6 levels of Bushfire Attack Level ratings. These levels correspond to the potential exposure of the site to heat flux exposure thresholds, expressed in kiloWatts per square metre (kW/m2).

In a bushfire, radiant heat levels are unsafe to humans and have the potential to ignite combustible materials in the vicinity. The higher the level of radiant heat intensity, as measured in kW/m2, the greater the exposure to risk. For instance, at 4 kW/m2, humans experience pain after 10 to 20 seconds. At 10 kW/m2, humans experience pain after 3 seconds. At 13 to 25 kW/m2, cotton fabric and timber ignite after a long time. At 45 kW/m2, timber ignites in 20 seconds, and at 55 kW/m2, timber ignites in only 10 seconds.

The 6 levels of BAL ratings are:

  • BAL Low:

At this level, the risk is considered to be very low. There is insufficient risk to warrant any specific construction requirements but there is still some risk.

  • BAL 12.5:

The risk is considered to be low. There is a risk of ember attack. The construction elements are expected to be exposed to a heat flux not greater than 12.5 kW/m2.

  • BAL 19:

The risk is moderate. There is a risk of ember attack and burning debris ignited by wind borne embers and a likelihood of exposure to radiant heat. The construction elements are expected to be exposed to a heat flux not greater than 19 kW/m2.

  • BAL 29:

The risk is considered to be high. 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. The construction elements are expected to be exposed to a heat flux not greater than 29 kW/m2.

  • BAL 40:

The risk is now very high. 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. The construction elements are exposed to a heat flux not greater than 40 kW/m2.

  • BAL Flame Zone:

The risk is considered extreme. 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. The construction elements are expected to be exposed to a heat flux greater than 40 kW/m2.

For more information

WA BAL Report are accredited Level 1 BAL Assessors and are experts at conducting Bushfire Attack Level Assessment Reports and bushfire prevention in general in Perth and Western Australia. For more information, contact our friendly staff on 08 6114 9356 or at admin@wabalreport.com.au.

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