 The interior of a CRT is evacuated to approximately  to , evacuation being necessary to facilitate the free flight of electrons from the gun(s) to the tube's face.The fact that it is evacuated makes handling an intact CRT potentially dangerous due to the risk of breaking the tube and causing a violent implosion that can hurl shards of glass at great velocity.As a matter of safety, the face is typically made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions, particularly if the CRT is used in a consumer product.