Fire-protective glass was developed in 1980.
It is made by laminating tempered glass with a layer of aqueous gel. When exposed to heat, the gel expands to form a foam that protects the outer glass layer and prolongs the period before the glass breaks.
It is always only a matter of time before standard window glass will shatter during a fire. And the fire will only spread faster once the glass cracks and falls out of the sash, making it more difficult to control the fire. Fire protective glass can withstand flames, smoke and heat radiation longer than standard glass.