Every warship that burned oil fuel had the capacity to create a smoke screen. This included every class of destroyer in service with the major powers of WWII. Oil burning ships could inject extra fuel into their furnaces, and reduce the supply of oxygen. The result was that the fuel would only partially combust. This produced dense clouds of black smoke from the funnels, forming a relatively effective smoke screen. Destroyers were also typically equipped with other means of making smoke (as the heat from the combustion tended to make smoke from the funnels rise). Royal Navy destroyers were equipped with a chemical smoke apparatus, using chlorosulphuric acid. When exposed the air, the acid reacted with the moisture in the air to form white smoke. This was piped out over the stern of the ship, to add to the smoke from the funnels. The smoke was discharged from three nozzles on the stern. Destroyers were also typically equipped with smoke floats. As the name suggests, these were floating smoke dischargers. These contained a mixture of chemicals that burned to create white smoke. Lit either with a built-in primer/igniter or a red-hot poker if the igniter failed, they could be used from their stowage position or thrown over the stern. A smoke float would burn for about ten minutes, and stay afloat for an hour before sinking. To create an effective smoke screen with floats, two would normally be used.