The tempered glass now used in sliding doors long ago replaced plate glass. Tempered glass consists of two layers: an inner tension layer and an outer compression layer. Able to resist heat, tempered glass also shatters into hundreds if not thousands of very small pebbles if stressed or broken. Plate glass sliding doors could be deadly because the glass stayed in large, sharp pieces. Nevertheless, a phenomenon known as spontaneous breakage can affect distressed tempered glass.
Today's sliding doors can withstand extreme heat because of their tempered glass. The two reasons that spontaneous breakage occurs are sustained damage and something called nickel-sulfide inclusion.
A pane of tempered glass can sustains damage during production, transit or installation. Even microscopic damage can cause very small cracks to begin to form. After time, the crack spreads and eventually the pane will explode.
It is possible that, during glass production, a small bit of metal did not fully melt down. If this happened, any number of factors, including temperature, could cause that metal to expand or contract, eventually shattering the glass. It would be a seemingly spontaneous break.
Unfortunately, for the owners of the sliding doors covered by warranty, both of these occurrences may be hard to prove. If this has happened to you and you are seeking compensation, you may have a difficult time proving that a spontaneous break occurred.