The Flames Stop Here

Advancements in glass manufacturing help prevent fire and smoke from spreading through a building.

In January, three students were killed and nearly 60 others were injured in a residence hall fire at Seton Hall University in New Jersey. What was particularly disconcerting about the tragedy was that students died even though the building's alarms activated properly to warn students.

But students had endured some 18 false alarms the previous semester, and many assumed that the noise blaring in the night was just another mistake. They went back to sleep, and deadly smoke from the fire spread through the halls and under their doors.

The Seton Hall tragedy is far from an isolated incident. Statistics from the National Fire Protection Association indicate that about 1,500 fires occur every year in campus housing.

The foremost lines of defense in preventing fires are sprinklers and alarms - they save lives and dramatically reduce the risks associated with fire. But they address only two issues: how to detect fires and how to suppress them. If they are less than 100 percent effective, an educational facility also should have elements in place to help contain the fire and smoke.

One of those elements is glass. Glass that is classified as "fire-rated" doesn't require any activation to contain flames. Whether installed in doors, sidelites, transoms or windows, fire-rated glass stands ready to help prevent the spread of fire.

Invisible barriers Sprinklers and alarms are considered "active" systems. To operate effectively, they require a number of steps to occur in the proper sequence. An unanticipated circumstance can impair the effectiveness of the entire system.

What happens if the water-supply valve is shut off? What if the water pressure drops? What if someone painted over the sprinkler heads during remodeling? Or, what if the PVC piping used for the sprinkler system melts during the fire?

Scenarios like those won't affect the fire defenses provided by fire-rated glass. It creates an invisible barrier to flames and smoke that ordinary window glass can't. When heated beyond 250øF, ordinary glass will shatter and leave an unobstructed path for fire and smoke to spread.

By way of contrast, fire-rated glass has been tested in conditions where the temperature exceeds 1,600øF. In a real fire, glass that has passed that kind of testing will remain intact and restrict the expansion of the fire. In some locations, glass often is more desirable than a solid material for enhancing lighting, security or aesthetics.

Typically, fire-rated glass is used instead of ordinary window glass in corridors, lobbies, stairwells and other areas of a building that could serve as an escape route during a fire.

The level of fire rating required is determined by several factors that could affect how long a person might be trapped in a burning building. For instance, the third floor of a hospital might have bedridden patients who would find it difficult to evacuate. In contrast, a single-story elementary school might empty very quickly.

Better products At one time, the only fire-rated glass on the market was polished wired glass. When people see the familiar criss-cross pattern in the glass, they may think it is there for safety or security. It isn't. The wire is embedded in the glass to hold it in place during a fire. But the wire does not make the glass stronger. In fact, wired glass is significantly weaker than ordinary tempered or laminated glass and can actually cause more injury when it is broken, because of the dangerous snags of broken wire.

Yet for many years, wired glass was the only glazing material that could endure the rigorous testing and earn a fire rating. It is a widely used product even today and can be found on the majority of school campuses in North America. But using wired glass to satisfy fire codes has often meant compromising impact safety. And after seeing injuries involving wired glass, some schools have learned the hard way that they may be held liable for such compromises.

Fortunately, a number of new glass options have emerged that outperform wired glass in both fire and impact safety. These glasses do not have wire mesh and help schools move away from the "institutional" look and feel of wired glass. With the growing awareness that environment affects learning, "wireless" fire-rated glass alternatives offer an improved aesthetic for schools and universities.

See-through ceramics One of the new product options isn't a glass at all: it is ceramic. For centuries, people have appreciated ceramic's high tolerance for heat. Today, sophisticated ceramic products can be found in stovetops, car engines and gas fireplaces, precisely because ceramic holds up well when things get hot.

Recognizing the value of that characteristic, manufacturers have developed a transparent ceramic for use in fire-rated openings. When it is installed, ceramic looks like ordinary window glass, yet it retains its heat-resistant qualities.

And while ordinary ceramics can be brittle, technology has produced fire-rated ceramic products with high-impact protection ratings. Available in insulated units for exterior applications, ceramic also can be beveled, etched or sandblasted without affecting the fire rating.

Ceramics have been tested to endure something else that is often overlooked: water. When water from a sprinkler or fire hose sprays onto hot glass, the glass is likely to shatter or explode. Standard glass cannot simultaneously handle the stress of two temperature extremes. Fire-rated ceramics, however, have passed what is called the "fire hose stream test" and are unaffected by this type of thermal shock.

Minimizing smoke Here is yet another example of why schools and universities should rely on more than sprinklers. Properly activated sprinklers may extinguish a fire, but in doing so they can generate large volumes of smoke. If water from the sprinklers has come in contact with hot, non-rated glass and the glass shatters, smoke will spread freely. And since the majority of fire-related deaths result from smoke inhalation rather than burns, there is still cause for concern - even after the fire is out.

In some cases, a school design may call for glass that can block heat in addition to flames and smoke. In stairwells, for instance, where people conceivably could become trapped during a fire for long periods of time, heat could quickly build up to an intolerable level if there were no means of keeping the temperature down. Historically, this has meant using solid barrier walls and only a small amount of glass for visibility as needed.

Recent advancements in fire-rated glass have made it possible to have unrestricted amounts of glass in locations with two-hour fire rating requirements. These newer glass products are called transparent wall units because they are tested to the same standards as walls, and they act as a barrier to the transfer of heat. Tests have shown that even with a hot fire on one side of the glass, the opposite surface of the glass is still cool enough to touch.

Transparent wall units incorporate a range of different technologies, but all work on essentially the same principle. Multiple layers of glass sandwich an inert material, which turns to foam during a fire. The foam obscures vision but blocks the heat of the fire.

Developments in fire-rated glass have created opportunities for school designers and architects looking to enhance their designs without sacrificing life safety. By using passive fire-rated glass in conjunction with active systems such as sprinklers and alarms, educational facilities can provide the best possible defense against a fire.

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