During the Han Dynasty, Taoist alchemists researching on an elixir for immortality caused many fires when they experimented with the ingredients sulphur and saltpetre (potassium nitrate). One of these alchemists later wrote an alchemy text, called Book of the Kinship of the Three, that warned against the mixing of certain materials.

By the 8th century during the late Tang dynasty, a formula for gunpowder was established. Made by combining saltpetre and sulphur with charcoal, gunpowder or 'huo yao' was first used to make fireworks and signal flares. Later simple hand-grenades were invented, which were thrown at the enemy using a catapult.

During the Song dynasty, gunpowder was used in rifles and rockets. The Song army also packed gunpowder into bamboo tubes and used it as a primitive form of flame-thrower.

In AD1126 a local official called Li Gang recorded the defence of the city of Kaifeng using cannons, inflicting heavy casualties on a marauding nomadic tribe.

Many early mixtures of Chinese gunpowder contained toxic substances such as mercury and arsenic compounds, and could be considered an early form of chemical warfare.