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.
Photo credit: Photo by Ron Moore
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 article 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