How Is Fire-Resistance Level Rating Calculated?

A fire resistance level (FRL) in Australian or Fire resistance rating (FRR) in New Zealand) is determined by submitting a product to the Standard Fire Test.  This fire test method is titled AS1530.4. Methods for Fire Tests on Building Materials, Components and Structures. The Standard Fire Test is based on IS834 Fire-resistance tests – Elements of building construction. The FRL or FRR fire-resistance rating tells us how long a passive fire protection system can withstand the three set criteria of Structural Integrity, Fire Integrity and Insulation.  The latter may be usefully described as Temperature Integrity as it is a time to failure of the barrier preventing heat transfer to prescriptive limits. a standardised test. As a result, the fire rating, as it is sometimes abbreviated,  is in terms of time (e.g. 60 minutes, 2-hour). and is expressed, in minutes in the following form Structural Integrity/Fire Integrity/Temperature Integrity.  A one hour fire rated  product would therefore be expressed as 60/60/60 or -/60/60 depending on whether it is load bearing or not.   In Australia, fire doors, fire shutters and some fire windows are given a Temperature Integrity concession and for a one hour fire rating, the products, depending on the application, need only provide a fire rating of -/60/30 in the case of fire doors or in the case of fire shutters and fire windows a fire resistance level of -/60/- .  Of course these products are typically non-load bearing, with the surrounding wall and the opening all required to be self supporting.  Although the passive fire protection system will fail after or even during the indicated time, it still allows for buying extra time to safely evacuate the occupants or for emergency responders to arrive  [please don’t refer to failure of the passive system before time.  This needs to be explained in context as covered below….].

Why are fire-resistance ratings useful

As mentioned above, the fire ratings are a result of standardised tests. There fire tests are required to be conducted by Registered Testing Authorities are official laboratories (as well as laboratories of the manufacturers of passive fire protection systems) that are accredited to operate run those very specific fire test furnacestests by using furnaces. These fire tests are intended to be repeatable so that the performance of products can be compared against one another.  The fire tests are not intended to and there is no direct correlation to show how the product may perform in a real building fire.  It is however, widely understood that a product that has been fire tested to a prescribed fire rating will resist fire and provide the fire compartmentation required to assist in the safe evacuation of a building.  In those tests, the researchers try to simulate what happens in an actual fire and even expose the materials beyond normal conditions. 

The Standard Fire Test method is conducted to a single specific Time-Temperature curve based on cellulosic fires.  Cellulosic fires are characterised by the burning of cellulosic products such as wood, paper and furnishings without the influence of other essential fire safety measures in the building, such as sprinklers, smoke exhaust, zone pressurisation and reduced fuel loads.

Under these standardised fire test conditions, it can be reasonably deduced that a product with a 2 hour fire resistance level will perform much better than a product with a 1 hour fire resistance rating when both are exposed to the same fire test.  

In New Zealand, for example, it is generally accepted that buildings with sprinklers will reduce the fire size and therefore the products need only satisfy the Fire Integrity rating or -/60/- for example.

Products used to protect openings in fire walls or floors with “partial insulation” may also be specified by the Fire Engineer when considering the efficacy of the complete fire safety design of the building.  Ultra Low Radiation (ULR) products can provide significant cost savings over fully insulated products (eg: -/60/60) but still provide excellent life safety performance.  These products need to be evaluated on a project by project basis by the Fire Engineer.  

The most reliable ULR products provide excellent insulating properties in the first 30 to 60 minutes in the Standard fire test.  This performance maintains fire compartmentation and tenability conditions, allowing sufficient time for the occupants to safely egress the building.  In the latter part of the fire test the products continue to provide sufficient fire compartmentation and prevent non-piloted ignition depending on the material type and distance from the barrier.  

Although conditions during an actual fire might go beyond expectations, the fire-resistance ratings are still useful in product certification. This means we can still feel confident and safe about those products with high ratings. Also, we’re able to know that the products have undergone rigorous testing. This also allows for easy comparison among the passive fire protection systems available in the market.

Those systems are often hidden and dormant during the normal days. However, during emergencies those fire protection systems should still work perfectly (which means saving lives and helping maintain the building’s integrity). Fire-resistance ratings and product certifications will help ensure those products will work as intended

It should be noted that a fire tested product is only part of the overall offering.  The product must be manufactured and installed in accordance with the fire test report.  Specifying passive fire protection products with 3rd party Accreditation, such as those with the Warnock Hersey Listing provide confidence that the product specified has not been substituted with inferior and non-compliant products..  Fire and Smoke Curtain products are already available in Australia and New Zealand that provide this independent 3rd part Accreditation.

Aside from choosing certified products with high resistance ratings in the first place, Of course, the longevity of passive fire protection systems, much like active fire protection systems, is easily extended by incorporating service and maintenance into every buildings Management in Use policies and programs.  it’s also important to have them inspected and maintained while they are installed in buildings. It’s possible that through the months and years a few issues might appear (which can compromise safety and compliance). Fire curtains, smoke curtains, fire resistant glazing, fire rated glass doors, smoke vents and other passive systems are easily maintained by competent technicians to ensure their integrity is not compromised.  might have deteriorated or that there are physical defects that compromise their integrity.

For the servicing, inspection and maintenance of passive smoke and fire control protection systems, our team is well-equipped to handle the task promptly and according to the highest professional standards. Through our more than 175 years of experience, we have arranged for quarterly, bi-annual and as-needed schedules for the maintenance of passive fire protection systems in modern buildings. Contact us today for more information.