AS 3959 and AS 1530.8.1 — Bushfire Attack Levels for Openings
AS 3959 sets construction requirements for buildings in bushfire-prone areas. For windows and doors the requirement is expressed as a Bushfire Attack Level (BAL), determined by vegetation, slope and distance. A tested system is the cleanest way to comply, because it replaces a long list of deemed-to-satisfy details with one report.
The six levels
BAL-LOW, BAL-12.5, BAL-19, BAL-29, BAL-40 and BAL-FZ. The numbers refer to the radiant heat flux in kW/m². Up to BAL-40 the exposure is ember attack, burning debris and radiant heat; at BAL-FZ there is direct flame contact. From BAL-40 the whole window assembly — frame, glass, seals and hardware — has to be assessed as a system rather than component by component.
Which test applies
AS 1530.8.1 covers BAL-12.5 to BAL-40 and simulates radiant heat at the relevant level, ember attack and burning debris, without continuous flame impingement. AS 1530.8.2 covers BAL-FZ and adds thirty minutes of the AS 1530.4 heating curve to represent direct flame contact.
What the test looks for
Over the 60-minute period the criteria include: no 3 mm probe penetration, no sustained flaming longer than 10 seconds on the unexposed face, radiant heat at 365 mm from the unexposed face not exceeding 15 kW/m², average and maximum temperature rises of 140 K and 180 K, and internal cavity temperatures within 250 °C and 300 °C between 20 and 60 minutes.
At a glance
- BAL-12.5 to BAL-40 tested to AS 1530.8.1
- BAL-FZ tested to AS 1530.8.2
- Aluminium screen mesh is not permitted at BAL-40
- Windows must also comply with AS 2047 and AS 1288
Common questions
Can we use an aluminium frame at BAL-FZ?
In practice it is very difficult. Aluminium loses strength well below the temperatures involved, so BAL-FZ assemblies usually rely on steel frames, non-combustible construction or a tested system with a protective screen. The BAL-FZ requirements are best confirmed with the project's bushfire assessor.
Does a BAL rating cover the whole window range?
A report covers the profiles, glazing build-ups and maximum sizes that were tested. Anything outside those limits needs a separate assessment, which is why the scope of the report matters as much as the rating itself.
Need a doorset that meets AS 3959 / AS 1530.8.1? Send us the project requirements.
Request a quoteOther standards
AS 1530.4 — Fire-Resistance Tests of Building Elements
The Australian method for determining the Fire Resistance Level (FRL) of walls, floors, doors and other building elements.
Read →EN 1634-1 — Fire Resistance Tests for Doors and Shutters
The European test for fire doors and shutters, used together with EN 1363-1 and classified under EN 13501-2.
Read →UL 10C — Positive Pressure Fire Tests of Door Assemblies
The North American door test, run under positive pressure and followed by a hose stream test.
Read →