Why did my tempered glass shatter when nobody touched it?
The most discussed cause is a nickel sulphide inclusion, a microscopic particle formed during glass manufacture. After tempering, it can slowly change phase and expand. If it sits in the tensioned core of the glass, that expansion can start a crack that releases the stored stress and shatters the whole pane. Other causes include edge damage, hard contact with metal fixings, impact, and thermal stress. A specialist can often tell which by examining the fracture origin.
From the RRD Field Guide, checked against the sources cited in Tempered Glass Breakage and Glass Railings in Singapore: Nickel Sulphide, Heat-Soak Testing and BCA Barrier Rules. General information, not advice for your project.
The fuller picture
Tempered glass can shatter without impact, months or years after installation, when a tiny nickel sulphide inclusion expands inside the glass. Heat-soak testing to EN 14179-1 reduces but does not eliminate this risk. In Singapore, BCA's acceptable solution requires glass in barriers to be laminated, barriers to be at least 1.0 m high, and tempered glass at height 2.4 m or more to be protected.
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