AN M18
The M18 Colored Smoke Grenade is a US Army grenade used as a ground-to-ground or ground-to-air signaling device, a target or landing zone marking device, or a screening device for unit maneuvering. The M18 replaced the World War II M15 which did not burn as long or as vividly. It is not designated the "AN-M18" but "M18." It can be seen repeatedly in the film Apocalypse Now (1979). It was discovered in Vietnam that the green smoke drove away swarming bees.
Potential hazard
With both the white AN-M8 and M18, there is a danger of starting a fire if it is used in a dry area. Expended smoke grenade canisters remain hot for some time after burning out and should not be picked up bare-handed. New smoke mixtures are under development that are less harmful if the smoke is inhaled for prolong periods. In enclosed spaces the smoke displaces oxygen and can cause respiratory or oxygen deprivation.
See also
United States hand grenades