Several of our previous posts have referenced “ballistic resistace” (or bullet resistance) as a key feature of high security doors. Without seeing it in action, it might be hard to picture how this works.

We’ve all seen ballistic resistant glass in movies or on tv. The bad guys open fire and their shots are stopped by a pane of glass, now covered in spider web cracks. We use a much less dramatic, but equally impressive technology behind our doors.
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On our UL level 8 (rifle) rated door, we sometimes utilize a “self-healing” system. The door is filled with ceramic pellets designed to absorb the impact of a round. As the round pierces the paneling or skin of the door, they crush the pellets behind it. Their energy is totally absorbed and the round won’t go any further. 

The aspect that is “self-healing” is that once those pellets get crushed, the pellets above begin to trickle down and fill in any gaps. The door acts almost like the hopper on a pitching machine, with pellets falling from top to bottom to replace those destroyed by bullet rounds. This is how the doors can withstand so many rounds in the same location without penetration.

This is a major advantage compared to ballistic glass or steel, which lack the self-healing properties of ceramics and therefore have a much lower failure threshold than ceramics.