With some automakers changing the type of glass used in side windows, experts say it's a good idea to know what type of windows your car has because it can affect your escape plan if the vehicle is in a water-related accident.
Tempered glass has been the standard on the side windows of cars for several decades, but some automakers are switching to laminated glass. Laminated glass, long the standard on front windshields, can now be found on the side windows of luxury, economy, American-made and foreign automobiles.
Laminated glass is basically two layers of glass fused together with plastic in the middle, which keeps the glass in one piece.
"It's more difficult to break. It can be almost impossible to actually penetrate," said engineer John Waskow of Architectural Testing, which tests glass used in buildings, including hurricane-resistant laminated glass.
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Laminated glass differs from tempered glass, which is designed to break in smaller, safer chunks.
The Enhanced Protective Glass Automotive Association says there are benefits to using laminated glass in side windows. It keeps the car quieter in the cabin and can be more fuel-efficient. It can keep would-be thieves out because penetrating it can be nearly impossible. For that same reason, it also can reduce injury to passengers from flying pieces of glass in accidents.
Plus, in rollover accidents, laminated glass can help save lives by keeping occupants inside of the vehicles, especially when used in combination with side-impact airbag curtains.
The EPGAA estimates that 12 percent of new cars built in 2013 will have laminated glass on the side front windows. By 2018, it will be 20 percent.
"If you wanted to keep you from being ejected from the vehicle in a rollover, the laminated glass is going to keep you in the vehicle," said Capt. Donny Dean, of the Fort Worth Fire Department Swift Water Rescue Team. "For escaping the vehicle, the laminated glass is going to be more difficult."
And in a water-related accident, the type of windows in a car could change the escape plan.
The NBC 5 Investigates Consumer Unit asked the Fort Worth Fire Department to help demonstrate the difference in how laminated and tempered glass breaks. The 2011 Chevrolet Malibu from a salvage yard used in the demonstration had tempered glass in the back-seat window and laminated glass in the front-seat window.
Firefighter Jake Sims easily broke the tempered glass window with a commercially available rescue hammer.
But the laminated glass was dramatically different.
Sims repeatedly banged on the laminated window with the same rescue hammer he used on the tempered glass. Strike after strike, the hammer fractured the glass, but the lamination held it together.
"I did not break the laminated glass," Sims said. "I wanted to punch through that, but I couldn't."
The National Highway Traffic Safety Administration told NBC 5 Investigates in a statement, "We believe that safety experts would agree that in a rollover, it is better to be retained in a vehicle than ejected. Occupants have a much higher rate of survival if they are not ejected. We are not aware of any data or studies that support a claim that occupants in a vehicle with laminated side windows are at greater risk related to drowning."
But the only way Sims could get out of the laminated window was to kick it out in one piece after it was fractured, and that's what you may have to do.
"The last situation you would put yourself in is to go ahead and be fully submerged and break the windows," Dean said.
"Break the Glass"
In November, a mother and her young daughter found themselves in that situation.
"Break the glass. Break the glass," a panicked Christina Williams told a 911 dispatcher after her car crashed into a Fort Worth pond in November with her toddler, Tisiphone, in tow.
Two young men driving by saw the accident unfold and jumped in to help.
"It all happened so quick," said John Piszor, a passer-by who stopped to see what he could do. "As soon as I got off the phone with 911, I jumped in there, and we swam out there and tried to help."
Piszor and his friend, Nathan Brown, worked frantically in the frigid water to free the mother and daughter.
"I started banging on the window and, in the back seat, I saw a baby, so I moved to the back and I tried to break the back window instead," Brown said.
As the car's front sank, Brown swam to the rear, kicking with all his strength and finally the back window broke open. He said he felt the child grab his finger, but he could not unbuckle her car seat.
Dive teams later pulled the mother and daughter from the submerged car. Neither survived.
"You don't want to call 911," Dean said. "You've got 30 seconds to a minute to evacuate the car, to get out."
It's best to escape while the car is above water, experts say.
"The first thing that you should do is unbuckle your seat belt and roll your windows down so you have a way to get out of the vehicle," Dean said.
Then, you should get passengers out and unbuckle any children.
"You want to evacuate your children from the oldest to the youngest," Dean said, which gives the children the greatest chance of survival.
The next step is to get out of the car.
Most sunroofs and rear windows are tempered.
To figure out what kind of glass is in the side window of your car, you can look in the bottom corner. There may be a label that says "tempered" or "laminated." If not, roll down the window and look at it from a bird's-eye view. If it's smooth and looks like one piece, it's tempered. If it looks like a sandwich with a ridge, it's laminated.
You can also call your automaker and ask.