An LC50 value is the concentration of a material in air that will kill 50% of the test subjects (animals, typically mice or rats) when administered as a single exposure (typically 1 or 4 hours). Also called the median lethal concentration and lethal concentration 50, this value gives you an idea of the relative acute toxicity of an inhalable material. This is closely related to the LCLo value which is the lowest concentration reported to have killed animals or humans. This value applies to vapors, dusts, mists and gases. Solids and liquids use the closely related LD50 value (50% lethal dose).