During the manufacturing of toughened glass microscopic pebbles (called nickel sulfide inclusions) can sometimes be trapped inside the glass. As the glass and pebbles expand and contract with the heat in the bathroom the pebbles can weaken the glass causing it to explode.

The most common reason is imperfections that arise during the tempering process. Although this is rare, over time these imperfections place a lot of stress on the glass, eventually leading it to shatter. Poor installation Another common cause that leads to shower glass exploding is improper installation.