Thermally Toughened glass is produced by heating annealed glass to high temperatures and then rapidly cooling to induce high compression in its surface. This pre-stressing produces a much stronger glass that will be less liable to break under impact or through thermal stress. When broken, toughened (or tempered) glass will fragment into small and comparatively harmless pieces. Toughened glass is considered as a "safety glass" and conforms to the British Standard BS6206 so that it can be used in all applications and locations. The toughening process does produce a certain amount of distortion and this can be noticeable over large pieces of glass. Small particles of Nickel sulphide can be present within the body of the glass and this can sometimes result in toughened glass shattering. By putting toughened glass through a further, heat soaking process the chance of this can be reduced. This is particularly used when glass is required in floors or balustrades.