Tempered or toughened glass is a type of safety glass that has been treated with controlled heat or chemical treatments to increase its strength compared to normal glass. Quenching puts the exterior surfaces in compression and the interior in tension. Such stresses cause glass, when broken, to crumble into small, granular pieces instead of shattering into jagged shards like flat glass. Granular lumps are less likely to cause injury. Because of its safety and strength, tempered glass is used in a variety of demanding applications, including passenger vehicle windows, shower doors, architectural glass doors and tables, refrigerator trays, cell phone screen protectors, as a component of bulletproof glass, for diving masks and various types of plates and kitchen utensils.