or potassium perchlorate. Sting Sting grenades, also known as stingball or sting ball grenades, are stun grenades based on the design of the fragmentation grenade. Instead of using a metal casing to produce shrapnel, they are made from hard rubber and are filled with around 100 rubber balls. On detonation, the rubber balls, and shrapnel from the rubber casing explode outward in all directions as a form of less-lethal shrapnel. These projectiles may ricochet. It is intended that people struck by the projectiles will receive a series of fast, painful stings, without serious injury. Some types have an additional payload of CS gas. Sting grenades do not reliably incapacitate people, so they can be dangerous to use against armed subjects. They can cause serious physical injury, especially the rubber shrapnel from the casing. People have lost eyes and hands to sting grenades. Sting grenades are sometimes called "stinger grenades", which is a genericized trademark as "Stinger" is trademarked by Defense Technology for its line of sting grenades. Chemical and gas type Chemical and gas grenades burn or release a gas, and do not explode. They include smoke and incendiary grenades. Smoke Smoke grenades are used as ground-to-ground or ground-to-air signaling devices, target or landing zone marking devices, and to create a smoke-screen for concealment. The body is a sheet-steel cylinder with emission holes in the top and bottom. These allow the smoke to be released when the grenade is ignited. There are two main types, one producing coloured smoke for signaling, and the other is used for screening smoke. In coloured smoke grenades, the filler consists of of coloured smoke mixture (mostly potassium chlorate, lactose and a dye). Screening smoke grenades usually contain HC (hexachloroethane/zinc) or TA (terephthalic acid) smoke mixture and white phosphorus (WP) and red phosphorus (RP). HC smoke contains hydrochloric acid and is harmful to breathe. These grenades can become hot enough to scald or burn unprotected skin, particularly the phosphorus type grenades. Riot control (pacification) Tear gas grenades are similar to smoke grenades in shape and operation. In tear gas grenades, the filler is generally of CS gas combined with a pyrotechnic composition which burns to generate an aerosol of CS-laden smoke. This causes extreme irritation to the eyes and, if inhaled, to the nose and throat. They were used in the Waco Siege. Occasionally CR gas is used instead of CS. Lethal Incendiary Incendiary grenades (or thermite grenades) produce intense heat by means of a chemical reaction. Seventh-century "Greek fire" first used by the Byzantine Empire, which could be lit and thrown in breakable pottery, could be considered the earliest form of incendiary grenade. The body of modern incendiary grenades is practically the same as that of a smoke grenade. The filler is of thermate, which is an improved version of World War II-era thermite. The chemical reaction that produces the heat is called a thermite reaction. In this reaction, powdered aluminium metal and iron oxide react to produce a stream of molten iron and aluminium oxide. This reaction produces a tremendous amount of heat, burning at . This makes incendiary grenades useful for destroying weapons caches, artillery, and vehicles. The thermite burns without an external oxygen source, allowing it to burn underwater. Thermite incendiary grenades are not intended to be thrown and generally have a shorter delay fuze than other grenades (e.g. two seconds). White phosphorus can be used as an incendiary agent. It burns at a temperature of . White phosphorus was used in the No 76 Special Incendiary Grenade by the British Home Guard and the No. 77 Mk. 1 grenade during