When you think of fire protection in a building, what comes to mind? Fire extinguishers? Smoke alarms? Sprinkler systems? Chances are that window glass wasn't at the top of the list. While fire-rated glass has been an important component in building safety for decades, most professionals in the industry know relatively little about it. As a result, it isn't difficult for the incorrect product to be specified, installed and approved - potentially putting lives and property at unnecessary risk.
We'll begin with some basic definitions. Just what is fire-rated glass? As the name implies, it is glass that has proven to offer a certain degree of protection in the face of fire. That may sound like a strange task for glass to perform. Obviously, glass can't extinguish a fire or warn a building's occupants that there's any danger. But fire-rated glass can help keep flames and smoke from spreading from one room to another. The official term for this is compartmentation, and it means that glass can play a vital role in restricting fire damage to a limited area.
To the casual observer, it would seem that any glass could do that. After all, fire-rated glass looks deceptively similar to its non-rated counterparts. However, in reality, most glass offers little, if any, fire protection. For instance, standard window glass will break when the temperature reaches approximately 250° F. Tempered glass can last until about 500°F. In contrast, fire-rated glass can typically survive heat in excess of 1600° F. That's a marked difference in performance. With structural fires capable of reaching extremely high temperatures very quickly, the need for this specialty glass is easy to recognize.
To earn its stripes, fire-rated glass must pass a battery of tests established by national test standards. Independent laboratories (such as U.L.) run the tests, then assign an appropriate rating based on the results. The ratings are time increments, reflecting the duration of testing the product endured. That duration is intended to correspond to the length of time the glass should be expected to perform reliably in a fire. So if a product has a 45 minute rating, theoretically you could count on it containing flames and smoke for the first 45 minutes of a fire.