Naphthalene is an organic compound with the chemical formula C10H8. It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings, making it a simple and rather symmetrical polycyclic aromatic hydrocarbon (PAH). It is the main ingredient of traditional mothballs.