Member of the U.S. Chemical Warfare fill M1 Frangible Grenade (FS) smoke bombs in the field. In September 1942 the United States standardized a Molotov cocktail-style device that was nominally designated as a "grenade". It consisted of a pint-sized clear glass bottle with a crimped metal cap. It was dubbed "frangible" because it was made of glass, which is brittle and easily broken. Most fillers were liquid compounds selected because they were activated by exposure to the air, thus not requiring a detonator. FS was a mixture of sulfur trioxide and chlorosulfuric acid that created a heavy, acrid screening smoke. The M1 Frangible Grenade (FS) was declared limited standard by 1944.