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BUILDING IN AREAS PRONE TO BUSHFIRES
The following has been taken from the Australian Standard AS3959-2009, which was updated following the Victorian bushfires in 2009. It prescribes minimum construction requirements based on the Bushfire Attack Level (BAL) of each site. The BAL’s are explained below;
|
BUSHFIRE ATTACK LEVEL (BAL) |
RADIANT HEAT EXPOSURE |
RISK LEVELS AND PREDICTED BUSHFIRE ATTACK LEVELS EXPLAINED |
|
BAL – LOW |
Insignificant |
The risk is very low. While there is still some risk, it is insufficient to warrant any specific construction requirements. |
|
BAL – 12.5 |
0 to 12.5 kW/m2 |
The risk is low. The main concern is a risk of ember attack. |
|
BAL – 19 |
12.5 to 19 kW/m2 |
Risk is considered moderate, with a risk of ember attack and burning debris ignited by wind borne embers. Likelihood of exposure to radiant heat. |
|
BAL – 29 |
19 to 29 kW/m2 |
Risk is considered high, with an increased risk of ember attack and burning debris ignited by windborne embers. Likelihood of exposure to an increased level of radiant heat. |
|
BAL – 40 |
29 to 40 kW/m2 |
Risk is considered very high. There is a much increased risk of ember attack and burning debris ignited by windborne embers, with an increased likelihood of exposure to a high level of radiant heat. Some possibility of direct exposure to flames from the fire front. |
|
BAL – FZ |
40 kW/m2 and above |
Risk is considered extreme, and an extremely high risk of ember attack and burning debris ignited by windborne embers. Likelihood of exposure to an extreme level of radiant heat and direct exposure to the flames from the fire front. |
|
BUSHFIRE ATTACK LEVEL (BAL) |
RADIANT HEAT EXPOSURE |
RISK LEVELS AND PREDICTED BUSHFIRE ATTACK LEVELS EXPLAINED |
|
BAL – LOW |
Insignificant |
The risk is very low. While there is still some risk, it is insufficient to warrant any specific construction requirements. |
|
BAL – 12.5 |
0 to 12.5 kW/m2 |
The risk is low. The main concern is a risk of ember attack. |
|
BAL – 19 |
12.5 to 19 kW/m2 |
Risk is considered moderate, with a risk of ember attack and burning debris ignited by wind borne embers. Likelihood of exposure to radiant heat. |
|
BAL – 29 |
19 to 29 kW/m2 |
Risk is considered high, with an increased risk of ember attack and burning debris ignited by windborne embers. Likelihood of exposure to an increased level of radiant heat. |
|
BAL – 40 |
29 to 40 kW/m2 |
Risk is considered very high. There is a much increased risk of ember attack and burning debris ignited by windborne embers, with an increased likelihood of exposure to a high level of radiant heat. Some possibility of direct exposure to flames from the fire front. |
|
BAL – FZ |
40 kW/m2 and above |
Risk is considered extreme, and an extremely high risk of ember attack and burning debris ignited by windborne embers. Likelihood of exposure to an extreme level of radiant heat and direct exposure to the flames from the fire front. |