Tornado Duo is made of borosilicate glass. There is no special treatment or coating. The glass is borosilicate glass.
Borosilicate glass is a type of glass that contains boron trioxide which allows for a very low coefficient of thermal expansion. This means it will not crack under extreme temperature changes like regular glass (i.e. Pyrex is made from borosilicate glass).
Borosilicate glass is also lead and BPA-free, making it perfectly food-safe.