Principle

When ordinary glass is exposed to fire, extreme temperature gradient is rapidly induced between fire side and non-fire side. Glass would break due to uneven distribution of heat across the glass after few minutes. Even though the glass is thermally tempered, it would break within 10 minutes.

When glass is undergone chemically strengthen ion exchange process for hours, coefficient of thermal expansion of this chemical strengthen glass is sharply reduced. It could resist much thermal shock caused by extreme temperature gradient across the glass between fire exposed and no fire exposed sides. Glass becomes molten but does not break under high temperature and high temperature gradient. It remains its integrity to keep away blaze, smoke and fume.