Current legislation permits the use of glass products in building, as glass has many positive attributes in terms of providing a fire-safe building. It is essentially non-combustible and, therefore, complies with all the regulations and requirements for the surface spread of flame. If insulated properly, the glass will not permit smoke to penetrate, nor will it produce smoke during the critical developing phase of a fire. Non-insulated glass rarely fails integrity in the center of the pane, but gaps may develop at the perimeter of the panel. Such gaps are normally associated with the deformation of the glazing system, and intumescent materials can compensate for this by expanding to fill any gaps that start to develop. When intumescent laminate reacts to fire and expands, it changes color from transparent to opaque.