A change went into effect for the 2015 International Building Code (IBC) (Ref. b) directing that monolithic non-laminated tempered glass can no longer be used in a handrail, guardrail, in-fill panel or a guard section. The 2015 IBC section 2407, in part, requires use of laminated glass which is fully tempered or heat-strengthened. There are exceptions, but they are limited to areas where there is no walking area below the glass railing. This code change was in response to several instances across North America of monolithic non-laminated glass spontaneously breaking. Monolithic non-laminated tempered glass is also subject to breakage by impact on its edges.
In November 2018 an incident of spontaneously breaking glass of an infill panel for a handrail occurred at Fort Hood Replacement Hospital. The design and construction of the hospital were prior to the code change. The primary causes of breakage have been determined to be nickel-sulfide (NiS) inclusions, or unprotected edges. Nickel-sulfide inclusions are imperfections in flat glass that have the potential to expand and cause the glass to break, often spontaneously. These NiS inclusions are not detectable by non-destructive methods. Currently, there are no known repair methods, so replacement or full encasement are the current known resolutions. Potential for spontaneous breakage due to NiS inclusions are rare. There are various industry studies on the topic. For an indication of the order of magnitude of probability, one industry study of destructive heat soak tests of samples of glass from 25,000 tons of glass shows the potential for spontaneous breakage is one break caused by a NiS inclusion per 8.7 tons of glass.