Fire doors, or fire rated doors, are one of the most important safety features of any building, but what exactly a fire door is can often be misunderstood.
In Australia, the National Construction Code dictates that all fire doors must be tested to certain specifications (i.e. AS1530.4) in order to meet resistance approvals and certification. After this they are given what is known as a “fire rating” or “fire resistance level” (FRL) – the latter being the correct terminology under the Building Code of Australia.
These two terms are commonly used interchangeably, however, they are actually not the same thing. The FRL of a door is made up of different components, not just the “fire rating”, and it is important to be able to understand and differentiate what these components are.
What Is a Fire Resistance Level?
Fire Resistance Level (FRL) as defined in the Building Code of Australia (BCA) is the grading period in minutes for three criteria: structural adequacy, integrity and insulation, tested to AS 1530.4-1990: “Methods for fire tests on building materials, components and structures – Fire-resistance tests of elements of building construction”.
The FRL is expressed like this: SA/INT/INS
What do these three criteria mean?
Structural Adequacy: The ability of a structure to maintain its stability and load-bearing capacity when tested in accordance with AS 1530.4. Failure of the structural adequacy of a door is deemed when the element collapses or when the rate of deflection for the element is in excess of prescribed limits.
Integrity: The ability of a door to resist flames and hot gases when tested in accordance with AS 1530.4. Failure of integrity is deemed when continuous flaming occurs on the non-exposed
side of the door, or when cracks or other openings through which flames can pass reveal themselves.
Insulation: The ability of a door to maintain a temperature below specified limits on the surface not exposed to flames below the limits specified, when tested in accordance with AS1530.4. Failure for the insulation criteria is deemed when the temperature rise of the non-exposed side exceeds predetermined thresholds.
Thus the FRL is determined by the number of minutes it takes before ‘failure’ of these criteria are deemed to have occurred.
For example, if a door has a required FRL of 60/90/60 is will need to maintain structural adequacy for 60 minutes, integrity for 90 minutes and insulation for 60 minutes, as tested to AS1530.4
If there is a dash where one of the figures is meant to be, this means that the criteria is non-applicable.
How Are Fire Doors Tested to Achieve a Fire Resistance Level?
Doors achieve their FRL through a series of stringent tests measuring their stability against a number of protection requirements. These are both active and passive tests:
• Passive fire protection tests assess the ability of the door set to contain fire, smoke and other gases during a fire.
• Active fire protection testing involves trialling certain devices/hardware that serve to operate in the event of a fire (for example: magnamatic devices that hold doors open)
The specific tests of each door will depend on a few characteristics:
• The material the door is made from.
• The particular fire resistant rating the door needs to meet (1 hour, 2 hour, 5 hour etc).
Doors are tested for flammability, combustibility, smoke/gas resistance and pressure resistance.
In Australia, fire doors and components can only be tested and certified by registered, accredited testing authorities like the CSIRO.
The National Association of Testing Authorities governs testing regulations and organisations in Australia.