There are two categories of fire-proof glass in Germany: F and G. The class indicates the amount of time in minutes that the glazing can resist a fire (i.e. 15, 30, 60, 120 and 360 minutes).
G rated glass offers protection against flames and smoke, but not heat. It is typically only used in interior areas and made of a single pane of glass with wire mesh inside.
F rated glass resists flames, smoke and heat and therefore helps to block and prevent the spread of all three. It consists of two to three panes covered with a special coating and is commonly used in labs, corridors and stairwells.
Even the best fire rated glass is useless if the supporting masonry is too weak for the type of glazing being used, or if too little insulation has been provided for fire protection. Therefore, both the wall and glass must have the same level of fire protection.
In order to resist both high temperatures as well as thermal shock, special glass is required. During a fire, a pane of glass is subject to extremely high temperatures and when the fire department arrives and suddenly sprays cold water on the building, the thermal shock would cause regular glass to explode.
Borosilicate glass, which most people know from microwave safe cookware for example, is used in windows and doors for fireproofing applications. It does not discolor due to heat and remains transparent, allowing rescuers to more easily see inside during an emergency.
The correct glazing should always be selected based both on its location and application since exterior facing windows have different requirements than internal windows for example.