Laminated glass is generally used for safety and security purposes. This is because even if the glass is broken, the PVB layers make the glass layers stick to them so that it does not fall out of the window frame. This is especially useful in households with small children. The PVB layers reduce the transmission of UV rays into the house, decreasing the likelihood of skin diseases. It is much more durable than ordinary glass even though its installation does not take any special effort or time. It can even resist impact by pieces of metal and rocks. Laminated glass is also much less vulnerable to changes in temperature and pressure than ordinary glass. The viscoelastic properties of the specialised PVB interlayer makes laminated glass an excellent sound insulator. This is an advantage if there are old people or pets inside the house.