Tempered glass should be thought of as shrink-wrapped energy. It is a solid glass that just wants to expand into many, many pieces. It wants to get out of its one-piece state and become lots of little pieces. For example, when you break tempered glass in a door window that has all its edges...
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The solution is to attempt to cover or blanket unframed glass so as you break it, the cover or blanket will help contain the unwanted movement of the glass shards. For a side window on an SUV or minivan, hold a blanket or tarp against the window to somewhat contain the glass shard movement.
A partially open door window glass also qualifies as an unframed window. Breaking this glass as is will cause a significant amount of glass to fly upward.
At the instant the surface tension of unframed tempered glass is released by breaking it with a rescue tool, the shards of glass expand somewhat violently in all directions.
Twisting of the notch of the Glas-Master Windshield Saw over the edge of the unframed glass accomplishes the same result as a spring-loaded center punch or any other glass-breaking tool.
Note the amount of flying tempered glass that is instantly produced as the unframed tempered-glass window is broken.
Notch in Glas-Master Windshield Saw tool is placed over edge of unframed side window glass on a minivan. Slight twist of saw will instantly shatter the glass.
Tempered glass should be thought of as shrink-wrapped energy. It is a solid glass that just wants to expand into many, many pieces. It wants to get out of its one-piece state and become lots of little pieces. For example, when you break tempered glass in a door window that has all its edges contained within a window or door frame, the glass typically breaks, but most of it remains intact within the door or window frame. You generally have to move the shattered glass pieces out of the window after it is broken.
Not so when breaking unframed tempered glass. Unframed window glass is commonly found on the side windows of minivans and SUVs. A door window that is partially open is also an unframed tempered-glass situation. At the moment unframed tempered glass is broken, it reacts instantaneously and expands in all directions, flying about the immediate area.
This University of Extrication column will familiarize you with the unique action that unframed tempered glass undergoes at the instant it is broken. Rescue personnel will be presented with a simple recommendation for safe and effective unframed glass management.
TASK: Given an unframed tempered-glass window on an acquired vehicle for training, the rescuer will break the tempered glass while controlling the movement of the unframed glass shards