Smokeless powder is a type of propellant used in firearms and artillery that produces less smoke and less fouling when fired compared to black powder. The combustion products are mainly gaseous, compared to around 55% solid products (mostly potassium carbonate, potassium sulfate, and potassium sulfide) for black powder. In addition, black powder leaves a thick, heavy fouling that is hygroscopic and causes rusting of the barrel. The fouling left by smokeless powder exhibits none of these properties (though some primer compounds can leave hygroscopic salts that have a similar effect; non-corrosive primer compounds were introduced in the 1920s). Despite its name, smokeless powder is not completely free of smoke; while there may be little noticeable smoke from small-arms ammunition, smoke from artillery fire can be substantial.
Originally invented in 1884 by Paul Vieille, the smokeless powder made autoloading firearms with many moving parts feasible (which would otherwise jam or seize under heavy black powder fouling). Smokeless powder allowed the development of modern semi- and fully automatic firearms and lighter breeches and barrels for artillery.
The most common formulations are based on nitrocellulose, but the term was also used to describe various picrate mixtures with nitrate, chlorate, or dichromate oxidizers during the late 19th century, before the advantages of nitrocellulose became evident.
Smokeless powders are typically classified as division 1.3 explosives under the UN Recommendations on the transportation of Dangerous goods – Model Regulations, regional regulations (such as ADR) and national regulations. However, they are used as solid propellants; in normal use, they undergo deflagration rather than detonation.
Before the widespread introduction of smokeless powder, the use of gunpowder or black powder caused many problems on the battlefield. Military commanders since the Napoleonic Wars reported difficulty with giving orders on a battlefield obscured by the smoke of firing. Verbal commands could not be heard above the noise of the guns, and visual signals could not be seen through the thick smoke from the gunpowder used by the guns. Unless there was a strong wind, after a few shots, soldiers using gunpowder ammunition would have their view obscured by a huge cloud of smoke. Snipers or other concealed shooters were given away by a cloud of smoke over the firing position. Gunpowder is a low explosive that does not detonate but rather deflagrates (burns quickly at subsonic speed). Gunpowder produces lower pressures and is about three times less powerful when compared to smokeless powder. Gunpowder is also corrosive, making cleaning mandatory after every use. Likewise, gunpowder’s tendency to produce severe fouling causes actions to jam and often makes reloading difficult.