AHJ PERSPECTIVE

BY RONNY J. COLEMAN

Ratings, Fire Testing and Standards – Part 3

Are you tired of testing yet? I hope not, because continued testing of materials and assemblies is absolutely critical to fire safety engineering. The future calls for more and more precise use of test data to support decisions that we make for approving installations. And our ability to understand the strength and weaknesses of the various systems used to describe products is going to be part of our professional lexicon for some time to come.

As a fire prevention regulator or code enforcer, you are going to see more

and more test results in the future, not less. For example, let's says your department is in an area where there is a wildland-urban interface problem. What does that mean about what you need to know about roof materials and testing? Is a Class A roof the same as a Class 1 roof? Unfortunately not. How can we tell the difference?

Standard Test Methods for Fire Tests of Roof Coverings UL 790 When we talk about fire safety and roofing most people only think of a fire involving roofs exposed to firebrands and ember showers. UL 790 covers the requirements for the fire resistance performance of roof coverings exposed to simulated fire sources originating from outside a building on which the coverings are installed. Think Urban-Wildland scenarios... or even large-conflagration fires in densely built-out cities. But, it is not the same as Class 1 roof. But, it is not the only way to look at roof assemblies.

UL 790 is designed to measure the relative fire characteristics of roof coverings exposed to simulated fire sources originating from outside of a building on which the covering has been installed. It is intended for installation on either combustible or noncombustible decks when the roof coverings are applied as intended. Testing to this standard results in a material being able to resist one of three classes of fire exposure. They are: Class A, Class B, and Class C.

Class A roof coverings are effective against severe fire test exposures. Under such exposures, roof coverings of this

class afford a high degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands.

Class B roof coverings are effective against moderate fire test exposures. Under such exposures, roof coverings of this class afford a moderate degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands.

Class C roof coverings are effective against light fire test exposures. Under such exposures, roof coverings of this class afford a light degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands.

When Class A roof coverings are effective against severe fire test exposures, they may or may not prevent the building from igniting. I have personally seen hundreds of Class A roofs lying atop rubble when fire gets into the attic space or the interior of the structure.

These fire test methods do not provide a basis to compare expected performance under all actual fire conditions, but they do provide a basis for comparison of the response of roof coverings when subjected to fire sources that are described herein.

The test to determine this level of safety is generically called "the burning brand" test, and it uses the three different test modules to determine the classification. You will note that there are three different sizes of "brands" that are being used to determine the