Safe Window Breaking—Types of Glass

I previously reviewed the Bust a Cap window-breaking device. Whether it is to extricate a car crash victim or make an emergency entry to a structure, you need to have good information if you are going to safely break a glass window or door.

There are three types of glass you will encounter: tempered glass, non-tempered glass, and laminated glass.

Tempered glass is heat-treated and is much stronger than non-tempered glass. Tempered glass is used where there is a likelihood of human contact and as such is made to shatter into small ¼” pieces when broken. The small pieces are not very sharp and safer to deal with than the next type.

Non-tempered glass is a different animal. When broken, non-tempered glass makes large, irregular, jagged pieces which are razor sharp. It is much more dangerous than tempered glass.

Laminated glass has plastic layers sandwiched between glass layers. Because of the plastic sheeting, it tends not to break, but be punctured under force. High impact is needed to defeat laminated glass, and fragmentation and spalling can occur which send small flakes and powdered glass inward.

Here are some rough generalizations about glass. Car side and rear windows, newer storefront windows, and modern sliding glass doors are made of tempered glass. Many building codes and laws require tempered glass be installed in residential and commercial doors and windows that are within 48” of doors.

Tempered glass normally has manufacturers watermarks at all four corners, but it can be ordered without the watermarks.

Non-tempered glass is most often encountered in ordinary residential windows, whether jalousie, casement, Miami-style, single or double hung.

Older sliding glass doors and older storefront windows were made from non-tempered glass and can kill you or cause severe lacerations when shattered. These break into very large, very heavy, and very sharp shards. I once worked for a window company and all of us dreaded replacing large non-tempered glass. It is extremely dangerous to work with.

Car windshields, skylights, and some commercial storefront doors and windows are constructed with laminated glass, which is the safest but toughest of the three glasses here. The problem is that you have to punch out the entire plastic sheet to clear the window and it can take some time.

Another type of laminated glass is wire glass. This is made for security purposes and is very hard to defeat, as the wire mesh is anchored to the window or door’s frame.

If you are unsure of the type of glass you are about to break and have time, wear gloves, eyewear, and protective gear. If you have to break out a large window in an older structure, I would not break it at the bottom. If it is non-tempered glass, it will rain down heavy fragments that will injure you badly.

The safest place to strike large glass is near an upper corner, while you are standing as far to the side of the window as you can. Once the glass is broken, use a longer item, like your baton or a long handled tool, to clear the glass from the opening. Pay particular attention to clearing out the glass above you.

Window punches used for car side glass are usually effective at a lower corner, and there is less danger from the safety glass when it comes down.

Many things can be used to break glass. There are better things than your baton. Do your best to respect the glass and use as much safety gear as you have available.

Finally, there is a fourth type of glass, but if you are attempting to bash out the bullet-resistant windows of a bank or your light armored vehicle, you need help. I mean, you really need help.

Randall is a twenty-three year sworn police officer in a mid-sized Florida police department. He has been an FTO, K9 Handler, Detective and SWAT Team Leader. He is currently the Midnight Shift K9 Sergeant and department SWAT Coordinator.

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Publisher at BlueSheepdog
Richard Johnson is a gun writer, police trainer and really bad joke teller. Check out his other writing on sites like Human Events, The Firearm Blog and Police & Security News.

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