The use of glass in buildings is very common and increasing as designers look to utilise its transparent properties. There are four main types: annealed, toughened, laminated and heat-strengthened. (These terms may vary in different countries, e.g. in North America “tempered” is used for glass with any form of heat strengthening, including toughened.) There are particular safety hazards associated with glass and these need to be a consideration in selection of type.
Normal glass breaks into shards, with obvious dangers. Laminated glass will also break, but the shards are held in place by the inner plastic layer. Toughened glass, too, will break, but it shatters into small pieces; hence its use in car windscreens.
This note focuses on a particular issue with toughened glass.