Alcohol-based versions typically contain some combination of isopropyl alcohol, ethanol (ethyl alcohol), or n-propanol.[4] Versions that contain 60 to 95% alcohol are most effective.[4] Care should be taken as they are flammable.[3] Alcohol-based hand sanitizer works against a variety of microorganisms but not spores.[4] Some versions contain compounds such as glycerol to prevent drying of the skin.[4] Non-alcohol based versions may contain benzalkonium chloride or triclosan.[8][9]