What is the glass of the fire hydrant box?
The fire hydrant box is not required to be made of glass. As long as it is made of non combustible material, do you mean the glass of the manual button in the box? It is not tempered, tempered is not easy to break.
This piece of glass is thin. It's about a millimeter. It's made of a special kind. When the fire to crack it, inside the button will automatically pop up, start switch alarm or directly start the fire pump.
