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Smoke grenades are canister-type grenades used as ground-to-ground or ground-to-air signaling devices, target or landing zone marking devices, or as screening devices for unit movements. Smoke grenades are normally considered non-lethal, although incorrect use may cause death. The body consists of a sheet steel cylinder with a four emission holes on top and one on the bottom to allow smoke release when the grenade is ignited. The filler consists of 250 to 350 grams of colored (red, green, orange, gray, yellow, blue, white, black, or violet) smoke composition (mostly potassium chlorate, lactose, and a dye). The reaction is exothermic and grenade casings will often remain scalding hot for some time even after the grenade is no longer emitting smoke. They are typically used for military purposes, but can be employed elsewhere safely, with non-lethal chemical compounds involved.
Another type of smoke grenade is the bursting variation. These are filled with white phosphorus (WP), which is spread by explosive action. White phosphorus catches fire in the presence of air, and burns with a brilliant yellow flame, while producing copious amounts of white smoke (phosphorus pentoxide). These double as incendiary grenades, and a variant of these are also launched from infantry-portable or armored fighting vehicle-mounted grenade launchers. Users must also be wary of wind direction when using smoke grenades.
Smoke grenades should not be confused with smoke bombs, which are typically started with an external fuse rather than a pin. Smoke grenades often cost around $40 USD compared to smoke bombs, which can often cost just a few cents. Smoke grenades generally emit a far larger amount of smoke than smoke bombs that are sold as fireworks.
Used to create smoke screens, the grenades can be used to provide opportunity for movement over ground covered by fire. Smoke grenades can also be used to signal aircraft. Thermal imaging is able to 'see' through normal smoke screens (not modern "multi-spectral" smoke screens) and troops with thermal imaging sights can use smoke to conceal themselves against hostile forces while still being able to see them using thermal cameras.
Smoke grenades are sometimes used in paintball or airsoft events, though these are not necessarily of military grade. Some devices utilized for the purpose of generating concealing smoke are high-volume smoke candles.
Smoke compositions can be also used as an aerosolization vehicle for other materials than dyes; popular applications are in dispersion of CN gas or more commonly CS gas, or in agriculture for dispersion of insecticides.