You may all heard that tempered glass has a tendency to shatter spontaneously due to NiS (Nickel Sulphide) inclusions that are predominantly found in raw materials used to make glass sheets. These inclusions are often too small to be detected and removed. To reduce the possibility of spontaneous breakage post installation, we recommend heat soaking of tempered glass prior to delivery. DDG’s heat soaking protocol follows the international Standard BS EN 14179-1:2005. Glass in building —. Heat soaked thermally toughened soda lime silicate safety glass to ascertain risk of spontaneous breakage. This provides greater assurance to building and owners on the use of tempered glass for their projects.