As seen in Life Safety Digest, October 2008
Inspecting Fire-Rated Glazing
Clear-cut labeling system helps ensure proper usage
By Jeff Razwick
Since many types of fire-rated and non-fire-rated glass look the same, effective inspection requires labels that fully disclose how any given product relates to the tested system according to laboratory directory and code requirements. This article will discuss the current fire rated glazing labeling system, how it relates to testing requirements, and the implications for life safety.
Labeling System Overview
The current marking system required by the 2006 International Building Code (IBC) and adopted by Underwriters Laboratories (UL) has three broad marking categories addressing:
- Suitability of product for use in various locations in a building
- Whether the fire rated glazing system has passed the required hose stream test
- Conformance with temperature rise criteria
In addition, a number indicates the fire rating period in minutes.
To show suitability for use in various locations in a building, the label includes one or more specific designations that describe where the system can be used:
- “D” indicates Doors
- “O” indicates Openings (sidelites, transoms, etc.)
- “W” indicates Walls
Performance on the hose stream test is indicated on the label by:
- “H” indicates glazing meets the HOSE STREAM test standards (required for ratings of 45 minutes or more)
- “NH” indicates glazing does NOT meet HOSE STREAM test standards (an NH marking is only appropriate for 20-minute fire-rated doors)
Likewise, conformance with temperature rise criteria is shown on the label with:
- “T” indicates glazing meets TEMPERATURE RISE criteria
- “NT” indicates glazing does NOT meet TEMPERATURE RISE criteria
Thus, a given label might read: “D-H-NT-45” for a product that can be used in doors, has passed the hose stream test, does not meet temperature rise criteria, and is fire-rated for 45 minutes. If the product is suited for additional locations, such as openings, a second line will be included with the appropriate marking categories.
While there are many potential permutations of the specific designation codes within the marking categories, the fact there are only three allows building owners and managers, compartmentation inspectors, code officials, specifiers, the fire service and others to note at a glance if a product is suited for a given use.
Labeling Clarity and Life Safety
The labeling system specifically shows at a glance whether a product has met all testing requirements (see sidebar “Fire-Rated Glazing Test Requirements”). One of the important – but often misunderstood – requirements is for the hose stream test.
The hose stream test is an important part of fire-rated glass testing, and the ICC’s Code Development Process has repeatedly reaffirmed this. U.S. standards require the hose stream test for all fire ratings of 45 minutes or greater. Canadian standards also require the test for all fire ratings.
The test involves spraying a heated glass and framing assembly with water from a fire hose at pressures and durations specified in NFPA 257 (National Fire Protection Association’s Standard on Fire Test for Window and Glass Block Assemblies). The test provides “a method for evaluating the integrity of constructions and assemblies and for eliminating inadequate materials or constructions.” (NFPA 257, B.11.4) The standards further state “the cooling, impact, and erosion effects of the hose stream provide important tests of the integrity of the specimen being evaluated.” To successfully pass the hose stream test, the glass and framing must remain intact and not separate from the frame, within limits specified in NFPA 257, B.12. Clearly, this test adds value as it makes the glazed wall subject to the same treatment as the wall, firestopping, fire dampers and fire doors.
So how does the test relate to life safety? NFPA 257, B.11.2 explains that spraying the glass and framing with water “provides a measure of its structural capabilities.” The standard explicitly acknowledges that weights have been used in Europe to test impact, but that the hose stream test provides greater uniformity and accuracy. In addition, the hose stream test evaluates the assembly’s ability to withstand thermal shock, such as might be experienced when hot glass is exposed to cool water from fire sprinklers or fire hoses. In essence, the hose stream test helps ensures that the glazing will not vacate the opening and create a path for the spread of flames and smoke.
The marking system also clearly indicates when a product has been adequately tested for heat transfer resistance. The “W” symbol for products suitable for walls indicates the product has been tested as a fire-rated wall according to ASTM E119. By their nature, such walls are fire-resistive.
There’s no doubt that it’s critical to make sure products provide fire-resistive protection where needed. Such products must be used in critical areas where people may be present for extended periods of time, including exit corridors and stairwells.
The professionals on the front lines of inspecting glazing installations are the critical players in all of this. As they know, labeling systems should be clear and easy to read, and provide sufficient details to inspect critical fire resistance rated effective compartmentation systems.
Jeff Razwick is the Vice President of Business Development for Technical Glass Products (TGP), a Snoqualmie, Washington-based supplier of fire-rated glass and framing systems, along with specialty architectural glass products. www.fireglass.com, 800-426-0279