What is Bush Fire Protection?
Bush fire Protection is the protection of buildings, as specified in the Australian Standard AS3959-2009 “Construction of buildings in bushfire-prone areas“, against burning embers, radiant heat or flame generated by a bushfire. The 2009 edition of AS 3959 explains Bushfire Attack Levels (BALs) as follows.
SCREENING REQUIREMENTS
| BAL | DESCRIPTION | SUITABLE MESH |
|---|---|---|
| 12.5 | Screens for windows and doors shall have a mesh or perforated sheet with a maximum | Aluminium, Bronze or Stainless steel |
| Aperture of 2mm, made of corrosion-resistant steel,bronze or aluminium. Gaps between | ||
| The perimter of the screen assembly and the building element to which it is fitted shall not | ||
| Exceed 3mm.The frame supporting the mesh or perforated sheet shall be made from metal | ||
| or bushfire resistant timber. | ||
| BAL 19 | Same as Above | Aluminium, Bronze or Stainless steel |
| BAL 29 | Same as Above | Aluminium, Bronze or Stainless steel |
| BAL 40 | Screens for windows and doors shall have a mesh or perforated sheet with a maximum | |
| Aperture of 2mm, made of corrosion-resistant steel or bronze. Gaps between | ||
| The perimter of the screen assembly and the building element to which it is fitted shall not | Bronze or Stainless steel | |
| Exceed 3mm.The frame supporting the mesh or perforated sheet shall be made from metal. | Bronze or Stainless steel | |
| BAL FZ | Same as Above | Bronze or Stainless steel |
Explaining the numbers:
- BAL – Low The risk is considered to be Very Low
- BAL – 12.5 (protection from ember attack and radiant heat up to and including 12.5kW/m²) there is a risk of ember attack. The risk is considered to be Low
- BAL – 19 (protection from ember attack and radiant heat greater than 12.5kW/m² up to and including 19 kW/m²) There is a risk of ember attack and burning debris ignited by wind borne embers and a likelihood of exposure to radiant heat. The risk is considered to be Moderate
- BAL – 29 (protection from ember attack and radiant heat greater than 19 kW/m² up to and including 29 kW/m²) There is an increased risk of ember attack and burning debris ignited by windbourne embers and a likelihood of exposure to an increased level of radiant heat. The risk is considered to be High
- BAL – 40 (protection from ember attack, increased likelihood of flame contact and radiant heat greater than 29kW/m² up to and including 40 kW/m²) There is a much increased risk of ember attack and burning debris ignited by windbourne 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 risk is considered to be very high
- BAL – FZ (protection from flame contact, together with ember attack and radiant heat of more than 40 kW/m²) 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 risk is considered to be Extreme
