Does heat-soak testing make tempered glass safe?
It reduces the risk but does not remove it. Heat soaking reheats tempered panes and holds them at a set temperature so that panes with critical inclusions break in the oven rather than on the building. Industry guidance states plainly that it will not eliminate spontaneous breakage. That is why BCA's acceptable solution still treats heat-soaked tempered glass at height as prone to spontaneous breakage and requires protection such as screens or shields.
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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