HURRICANE-RESISTANT GLASS: FIREFIGHTER-RESISTANT?
BY MICHAEL T. REIMER
In the aftermath of Hurricane Andrew in August 1992, South Florida faced extensive property loss and the immediate challenge of rebuilding damaged structures and designing new buildings to withstand hurricane-force winds. Government officials realized they needed to review existing building codes. Even though South Florida codes were already among the most stringent in the nation, weather patterns in the area created the need for serious revisions.
Preserving the building`s envelope is the critical first line of defense in preventing severe damage throughout a structure. Existing codes address only the need for wind resistance, not the problem of windborne debris and its role in breaching the integrity of the building or subsequent damage from water.
One manufacturer addressing these standards has produced a new type of laminated glass for residential and commercial buildings. This material, manufactured by DuPont, is a three-layer composite called “SentryGlas®” that would be factory-laminated to a single piece of standard glass. SentryGlas® composite combines an interlayer of Butacite PVB film, a polyester film, and an abrasion-resistant hard coating that provides long-term durability.
THE TESTS
Testing windows for code compliance is done in two parts. The following explains the process used for certification.
Part 1. Position three glass windows opposite an air cannon containing a nine-pound 2 3 4. Each window must resist a nine-pound 2 3 4 fired twice from a cannon at 50 feet per second (34 miles per hour). Each of the three windows has different target impact points in strategically located areas of the glass and sash. To pass, the three windows must resist penetration by the 2 3 4.
Part 2. The already impacted windows are subjected to cyclic pressure testing. A machine creates a cycle of push/pull forces at variable strengths to replicate the strong positive and negative pressure of hurricane winds. The test is designed to simulate hurricane-force winds gusting against a building as the eye of the storm passes. To pass, the window system must remain in its frame and not allow an opening beyond a specific size (for example, in Dade County, Florida, the tear can be only five inches long by 116 inch wide).
EFFECTS ON FIREGROUND OPERATIONS
Modern technology so often requires adaptation on the fireground. Traditional ventilation and forcible-entry methods may be rendered ineffective on these new high-tech materials. Prompt ventilation is the key for saving lives, suppressing fire, and reducing damage. As a result of the increased use of plastics and other synthetic materials, the fuel load in most occupancies has also increased. The products of combustion produced during fires are becoming more dangerous and are being produced in larger quantities than ever before. Laminates on windows will have an impact on the ability to perform these actions in a timely manner.
Determining the presence of these laminates is very difficult. In smoke and fire conditions, there are no indicators that these protective films are in place. When given the task of horizontal ventilation at a residential structure, standard glass-breaking techniques that firefighters have relied on for decades will not be effective. Skills we learned in recruit training such as striking the window with the tool at the top of the pane will not be the method of choice on windows equipped with this material. Windows with laminates installed should be treated as laminated safety glass found in most automotive windshields. This product in fact was used for windows in many Cadillacs in the early 1980s.
Although it is time-consuming, this glass can be removed effectively by chopping with the blade of a standard fire department flathead axe or pneumatic glass-removal saws. Manual glass-removal saws also proved to be effective but often fatigued the firefighter if multiple windows were involved. One setback when using these specialized glass saws is that they were designed specifically for use during automotive extrication and do not allow firefighters to be distant from the window during removal, possibly subjecting them to venting heat and flame. Another concern is the clearing of the windows after the glass has been removed to allow firefighters to enter and victims to be rescued. The pneumatic glass saw appeared to leave the edge smoother than the other methods, reducing the chance of injury should the window become a point of entry or exit.
Products such as SentryGlas® no doubt will save scores of human lives in a natural disaster. However, such technological breakthroughs also present a difficult challenge for firefighters. We must stay abreast of changes occurring within the construction industry that affect our operations and safety. The development of new and innovative products may require the development of new or revision of current standard operating guidelines. The key to a successful operation is acquiring an increased knowledge base before the incident. Preplanning your first-due run area to determine the builders who are installing these products in new construction developments will greatly enhance your performance on the fireground. Training with these new products in a controlled environment may affect the decisions you make at an actual emergency. These split-second decisions can save lives. n
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(Top left) A firefighter attacks the glass with a manual glass-removal saw–a labor-intensive operation if multiple panes are encountered. (Bottom left) A pneumatic saw with glass-cutting blade is very effective; but, like the manual saw, it necessitates the firefighter`s being close to the window–a possible hazard. (Right) When using an axe, short, chopping strokes are preferred, in similar fashion to that of removing laminated safety glass windshields on automobiles. Care must be taken not to bury the axe head in the laminate–it becomes difficult to remove and creates further venting delay. (Photos by author.)
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Formal and informal breakability tests on hurricane glass. The DuPont test (left) subjects the glass to a 2 3 4 shot out of an air cannon at 34 mph. It cracks the glass exterior but does not penetrate. Inside, the glass is smooth and intact. The glass also could not be penetrated with repeated home-run swings (right). (Photos courtesy of DuPont.)
REMOVING HURRICANE GLASS
1. Preplan your first-due run area. Become familiar with developments that are installing this glass.
2. Acquire a piece of blemished glass for training, and practice the methods described below.
3. Size up the window to see if it is locked.
4. With the broad side of a flathead axe (prevents the head from becoming buried in the laminate), attempt to break the top third of the glass.
5. If spidering occurs, make short, chopping strokes along the edges with a flathead axe or pneumatic or manual glass-removal saw to remove the glass.
6. Be aware of the residual glass left in the frame. It may be a hazard if entry is made for rescue.
7. Experiment with other techniques on the training ground. Some firefighters have had success with chain saws and carbide-tip power saws. Also, explore techniques to remove the window frame. n
MICHAEL T. REIMER is a firefighter assigned to Special Operations with the City of West Palm Beach (FL) Fire Department. He is an adjunct instructor for the National Fire Academy and a rescue officer for the FEMA FL-TF II USAR Team. He has a bachelor`s degree in fire and safety engineering from the University of Cincinnati and is a member of the new NFPA Committee on Technical Rescue.
